I have seen multiple servers with this when you go into the multiplayer panel and hover over the player count this shows up: (If anyone knows how to do it please tell me how or add me on skype and show me how: byronsmall.1)

If you want an example add this server to your server list and hover over the player count: pvp.FusionRush-MC.com

If you want an example add this server to your server list and hover over the player count: pvp.FusionRush-MC.com
4
In 1.7, you can see who is in a server by hovering your mouse over the player count. They have manipulated this feature with plugins to show you their set text. I'm making a plugin on this soon, so you'll be able to do this on your own server :3
I have searched. I have not found XD
Basically, they have a plugin, or something that sets the playerlist to that. You might be able to search bukkit for something that'll do that.
Probably just a bug, or a plugin.
