In "Bug In Mouth Disease", when Strong Bad is duct-taped to the TV, there are five pieces of tape. But when he turns around, there are only four.
In "Marshmallow's Last Stand", Homestar's star has five points, but when Strong Bad tears it up, it appears to be torn into four triangular pieces.
In "Cool Things", when he wears the cool shades, the paint drips off the lens over Homestar's right eye, but the drops fall in front of the left side of the mouth and the paint disappears half way down his face.
In "Halloween Potion-ma-jig", when Strong Bad's Jambi costume's cabinet doors are open, they appear to be symmetrical; they should not be able to fit together when closed.
In "In Search of the Yello Dello", during the scene where Pom Pom and Homestar are supporting Strong Sad so he can tell his story, Homestar wakes up and slides out from underneath Strong Sad, yet Strong Sad doesn't move (he was previously standing on top of Homestar).
In "Homestarloween Party", the flashlight has a sliding switch, but makes the sound of an on/off button.
In "3 Times Halloween Funjob", when Strong Sad chants "Credenza" with the rest of the group, his mouth doesn't move.
In "Cheat Commandos...O's", Silent Rip and Fightgar's mouths do not move when they shout with the rest of the Commandos, "We're saved!"