The Evil Bug is a small bug that was created from Timmy's wish to get rid of Vicky the Babysitter's evil personality.
This creature was first introduced in "Vicky Loses Her Icky" after Timmy wished that Vicky would be nicer. After the wish, her evil left her body as a bug that lived in her butt.
Its appearance is a black beetle with red eyes, large pincers and a white skull on its abdomen. Using its pinches, it can attach itself to the buttocks of any person it chooses, causing them to become evil. If the bug is removed from the current host it is in, it will search for a new host.
After Timmy wished for Vicky to be a nice person, her evil left her body in the form of a bug (possibly a tick or a beetle) that had crawled up her butt. The bug sought out other hosts as it needs to find a new host to reside in. The bug sought out Mr. Turner, Principal Waxelplax, and finally, The President of the United States as hosts; but was stopped when Vicky lept in front of the President and the bug went back up her skirt and into her butt. Vicky apparently wasn't wearing any panties as the bug went right back up her butt, which it could not have if Vicky was wearing underwear.