An interesting bug was discovered by players last summer. This bug has been circulating the Net and now thousands of people are aware of it. The bug allows a character to "desync" with the game world and then to cast an army of minipets (including multiple copies of the same pet). Then when they resync, they're surrounded by a veritable swarm of vanity pets. However, the downside is the additional lag it causes to every player on the server.
People have been requesting that I post how to do this on the site, but I will not do so. The community should understand that this is considered a "known exploit" by Blizzard and as such, if a GM sees a player using this bug, his/her account could be suspended. My advice is to refrain from using this bug. It may look cool, but it's not an intended feature of the game.