First, you need a nametag. Name it jeb_ with an anvil, then right click a sheep with it. Immediately it will start to slowly change colour. You now have a rainbow sheep. Though if you rename it, it won't do this anymore.

A ton of you use commands in the chat filter, but what if a block did it all for you? First, enter the command give into chat. Then, enter in @whatever-your-username-is command_block after it. You will be given a block that has colour dots in the middle of its sides. Right click on it. Then, you can enter any command you like!
Command: /give @your-username command_block

You can defeat the Ender Dragon- but did you know you can spawn it IN THE OVERWORLD? First, you have to type into the chat filter: /summon. Then, you must enter EnderDragon. After that, press ENTER and you will have an Ender Dragon as a pet! It does 0 damage, so that's why I said you can keep it as a pet.
Command: /summon EnderDragon