You can summon a Crab without any mod or resource pack using the command below.

To spawn a Crab, you have to obtain a Crab Spawn Egg. You have to throw shears and an egg to the ground to make a Crab Spawn Egg or right-click on the sign on the side of the command box that is written: "[​GIVE EGG]".

Watch on Youtube: https://youtu.be/U3lfJcgOe1U
Official command: https://torchcraftyt.github.io/Commands/Crab.html

---

Triple-click to select all the commands then right-click and choose copy. Next, get in your world, and give yourself a command block (using /give @s command_block). Paste the command in the command block (using Ctrl+C or Cmd+C). Finally, place a Redstone block next to the command block.

summon minecraft:falling_block ~ ~1 ~ {"BlockState":{"Name":"redstone_block"},"Time":1,"Passengers":[{"id":"villager","Health":0,"Passengers":[{"id":"falling_block","Time":1,"BlockState":{"Name":"activator_rail"},"Passengers":[{"id":"command_block_minecart","Command":"gamerule commandBlockOutput false"},{"id":"command_block_minecart","Command":"fill ~1 ~-2 ~0 ~6 ~-2 ~4 minecraft:blue_concrete"},{"id":"command_block_minecart","Command":"fill ~1 ~-2 ~1 ~1 ~-2 ~3 minecraft:white_terracotta"},{"id":"command_block_minecart","Command":"fill ~1 ~-1 ~0 ~6 ~-1 ~4 minecraft:blue_stained_glass"},{"id":"command_block_minecart","Command":"fill ~1 ~0 ~0 ~6 ~0 ~4 minecraft:blue_concrete"},{"id":"command_block_minecart","Command":"setblock ~1 ~0 ~0 minecraft:black_concrete"},{"id":"command_block_minecart","Command":"setblock ~1 ~0 ~1 minecraft:white_concrete"},{"id":"command_block_minecart","Command":"setblock ~1 ~0 ~3 minecraft:white_concrete"},{"id":"command_block_minecart","Command":"setblock ~1 ~0 ~4 minecraft:black_concrete"},{"id":"command_block_minecart","Command":"setblock ~0 ~-1 ~1 minecraft:oak_wall_sign[facing=west,waterlogged=false]{back_text:{color:\"black\",has_glowing_text:0b,messages:['{\"text\":\"\"}','{\"text\":\"\"}','{\"text\":\"\"}','{\"text\":\"\"}']},front_text:{color:\"black\",has_glowing_text:0b,messages:['{\"text\":\"\"}','{\"color\":\"dark_blue\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"give @s minecraft:phantom_spawn_egg{EntityTag:{id:marker,Tags:[crab-spawner]},display:{Name:\\'[{\\\\\"text\\\\\":\\\\\"Crab Spawn Egg\\\\\",\\\\\"italic\\\\\":false}]\\'}}\"},\"text\":\"[GIVE EGG]\"}','{\"text\":\"\"}','{\"text\":\"\"}']},is_waxed:1b}"},{"id":"command_block_minecart","Command":"setblock ~0 ~-1 ~2 minecraft:oak_wall_sign[facing=west,waterlogged=false]{back_text:{color:\"black\",has_glowing_text:0b,messages:['{\"text\":\"\"}','{\"text\":\"\"}','{\"text\":\"\"}','{\"text\":\"\"}']},front_text:{color:\"black\",has_glowing_text:0b,messages:['{\"text\":\"Crab\"}','{\"text\":\"Command box\"}','{\"text\":\"Made by\"}','{\"text\":\"TorchCraft\"}']},is_waxed:0b}"},{"id":"command_block_minecart","Command":"setblock ~0 ~-1 ~3 minecraft:oak_wall_sign[facing=west,waterlogged=false]{back_text:{color:\"black\",has_glowing_text:0b,messages:['{\"text\":\"\"}','{\"text\":\"\"}','{\"text\":\"\"}','{\"text\":\"\"}']},front_text:{color:\"black\",has_glowing_text:0b,messages:['{\"text\":\"\"}','{\"color\":\"dark_red\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"fill ~ ~-1 ~-3 ~6 ~1 ~1 air\"},\"text\":\"[UNINSTALL]\"}','{\"text\":\"\"}','{\"text\":\"\"}']},is_waxed:0b}"},{"id":"command_block_minecart","Command":"setblock ~5 ~-1 ~3 minecraft:repeating_command_block[conditional=false,facing=west]{Command:\"execute as @e[type=minecraft:marker,tag=crab-spawner] at @s run summon pig ~ ~ ~ {Tags:[crab],HandItems:[{id:shears,tag:{display:{Name:'[{\\\"text\\\":\\\"Crab claw\\\",\\\"italic\\\":false}]'}},Count:1}],HandDropChances:[1f],Silent:1b,active_effects:[{id:\\\"minecraft:invisibility\\\",duration:999999,show_particles:0b}],DeathLootTable:\\\"minecraft:empty\\\",CustomName:'[{\\\"text\\\":\\\"Crab\\\"}]',Passengers:[{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:blue_concrete_powder\\\",Properties:{}},transformation:[0.3750f,0.0000f,0.0000f,-0.1875f,0.0000f,0.2500f,0.0000f,-0.7776f,0.0000f,0.0000f,0.5000f,-0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:white_terracotta\\\",Properties:{}},transformation:[0.3000f,0.0000f,0.0000f,-0.0875f,0.0000f,0.1250f,0.0000f,-0.7876f,0.0000f,0.0000f,0.4000f,-0.2000f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:white_concrete\\\",Properties:{}},transformation:[0.0100f,0.0000f,0.0000f,0.1875f,0.0000f,0.1250f,0.0000f,-0.5901f,0.0000f,0.0000f,0.1000f,-0.1800f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:white_concrete\\\",Properties:{}},transformation:[0.0100f,0.0000f,0.0000f,0.1875f,0.0000f,0.1250f,0.0000f,-0.5901f,0.0000f,0.0000f,0.1000f,0.0800f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:black_concrete\\\",Properties:{}},transformation:[0.0100f,0.0000f,0.0000f,0.1885f,0.0000f,0.0500f,0.0000f,-0.5151f,0.0000f,0.0000f,0.0500f,-0.1800f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:black_concrete\\\",Properties:{}},transformation:[0.0100f,0.0000f,0.0000f,0.1885f,0.0000f,0.0500f,0.0000f,-0.5151f,0.0000f,0.0000f,0.0500f,0.1300f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[0.3000f,0.0000f,0.0000f,-0.0500f,0.0000f,-0.1500f,-0.2598f,-0.5876f,0.0000f,0.2598f,-0.1500f,0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[0.3000f,0.0000f,0.0000f,-0.1500f,0.0000f,-0.1500f,-0.2598f,-0.5876f,0.0000f,0.2598f,-0.1500f,0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[0.3000f,0.0000f,0.0000f,-0.2500f,0.0000f,-0.1500f,-0.2598f,-0.5876f,0.0000f,0.2598f,-0.1500f,0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[0.3000f,0.0000f,0.0000f,-0.0500f,0.0000f,-0.1500f,-0.2598f,-0.5876f,0.0000f,0.2598f,-0.1500f,0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[0.3000f,0.0000f,0.0000f,-0.1500f,0.0000f,-0.1500f,-0.2598f,-0.5876f,0.0000f,0.2598f,-0.1500f,0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[0.3000f,0.0000f,0.0000f,-0.2500f,0.0000f,-0.1500f,-0.2598f,-0.5876f,0.0000f,0.2598f,-0.1500f,0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[-0.3000f,0.0000f,-0.0000f,0.0375f,0.0000f,-0.1500f,-0.2598f,-0.5876f,-0.0000f,-0.2598f,0.1500f,-0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[-0.3000f,0.0000f,-0.0000f,0.1375f,0.0000f,-0.1500f,-0.2598f,-0.5876f,-0.0000f,-0.2598f,0.1500f,-0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:block_display\\\",block_state:{Name:\\\"minecraft:lightning_rod\\\",Properties:{facing:\\\"down\\\",powered:\\\"false\\\"}},transformation:[-0.3000f,0.0000f,-0.0000f,0.2375f,0.0000f,-0.1500f,-0.2598f,-0.5876f,-0.0000f,-0.2598f,0.1500f,-0.2500f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:item_display\\\",item:{id:\\\"minecraft:shears\\\",Count:1},item_display:\\\"none\\\",transformation:[-0.2121f,0.0000f,0.2121f,0.2500f,0.0549f,0.2898f,0.0549f,-0.6676f,-0.2049f,0.0776f,-0.2049f,0.3000f,0.0000f,0.0000f,0.0000f,1.0000f]},{id:\\\"minecraft:item_display\\\",item:{id:\\\"minecraft:shears\\\",Count:1},item_display:\\\"none\\\",transformation:[-0.4330f,0.0000f,-0.2500f,0.3000f,0.0647f,0.4830f,-0.1121f,-0.5876f,0.2415f,-0.1294f,-0.4183f,-0.3400f,0.0000f,0.0000f,0.0000f,1.0000f]}]}\",CustomName:'{\"text\":\"@\"}',LastExecution:544864L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~4 ~-1 ~3 minecraft:chain_command_block[conditional=false,facing=west]{Command:\"/kill @e[type=minecraft:marker,tag=crab-spawner]\",CustomName:'{\"text\":\"@\"}',LastExecution:545029L,LastOutput:'{\"extra\":[{\"color\":\"red\",\"extra\":[{\"translate\":\"argument.entity.notfound.entity\"}],\"text\":\"\"}],\"text\":\"[22:47:03] \"}',SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~3 ~-1 ~3 minecraft:chain_command_block[conditional=false,facing=west]{Command:\"/execute as @e[tag=crab] at @s on passengers run data modify entity @s Rotation[0] set from entity @e[distance=0,limit=1] Rotation[0]\",CustomName:'{\"text\":\"@\"}',LastExecution:545091L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~2 ~-1 ~3 minecraft:chain_command_block[conditional=false,facing=north]{Command:\"/execute as @e[tag=crab] at @s on passengers run tag @s add crab-body\",CustomName:'{\"text\":\"@\"}',LastExecution:545291L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~5 ~-1 ~2 minecraft:chain_command_block[conditional=false,facing=north]{Command:'/execute as @e[type=item,nbt={Item:{id:\"minecraft:egg\"}}] at @s if entity @e[type=item,nbt={Item:{id:\"minecraft:shears\"}},distance=..1] run tag @s add crab-spawn-egg',CustomName:'{\"text\":\"@\"}',LastExecution:545359L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~4 ~-1 ~2 minecraft:chain_command_block[conditional=false,facing=east]{Command:\"/execute as @e[tag=crab-body,tag=!alive] run kill @s\",CustomName:'{\"text\":\"@\"}',LastExecution:545429L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~3 ~-1 ~2 minecraft:chain_command_block[conditional=false,facing=east]{Command:\"/execute as @e[tag=crab] at @s on passengers run tag @s add alive\",CustomName:'{\"text\":\"@\"}',LastExecution:545516L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~2 ~-1 ~2 minecraft:chain_command_block[conditional=false,facing=east]{Command:\"/execute as @e[tag=crab-body] run tag @s remove alive\",CustomName:'{\"text\":\"@\"}',LastExecution:545571L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~5 ~-1 ~1 minecraft:chain_command_block[conditional=false,facing=west]{Command:\"execute as @e[tag=crab-spawn-egg] at @s run particle happy_villager ~ ~.5 ~ 0.2 0.2 0.2 5 10\",CustomName:'{\"text\":\"@\"}',LastExecution:545646L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~4 ~-1 ~1 minecraft:chain_command_block[conditional=false,facing=west]{Command:'execute as @e[tag=crab-spawn-egg] at @s run kill @e[type=item,nbt={Item:{id:\"minecraft:shears\"}},distance=..1,limit=1]',CustomName:'{\"text\":\"@\"}',LastExecution:545714L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~3 ~-1 ~1 minecraft:chain_command_block[conditional=false,facing=west]{Command:\"execute as @e[tag=crab-spawn-egg] run data merge entity @s {Item:{id:phantom_spawn_egg,tag:{EntityTag:{id:marker,Tags:[crab-spawner]},display:{Name:'[{\\\"text\\\":\\\"Crab Spawn Egg\\\",\\\"italic\\\":false}]'}}}}\",CustomName:'{\"text\":\"@\"}',LastExecution:545775L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~2 ~-1 ~1 minecraft:chain_command_block[conditional=false,facing=west]{Command:\"execute as @e[tag=crab-spawn-egg] run tag @s remove crab-spawn-egg\",CustomName:'{\"text\":\"@\"}',LastExecution:545839L,SuccessCount:0,TrackOutput:1b,UpdateLastExecution:1b,auto:1b,conditionMet:1b,powered:0b}"},{"id":"command_block_minecart","Command":"setblock ~ ~1 ~ command_block{Command:\"fill ~ ~ ~ ~ ~-3 ~ air\",auto:1}"},{"id":"command_block_minecart","Command":"kill @e[type=command_block_minecart,distance=..1,tag=!debug]"}]}]}]}