Continuity mistake: Look carefully at the brochure Frank has about the Buffalo Chicken Wing festival, the building pictured is the same building as his daughter's school (seen earlier in the movie).
Suggested correction: While the buildings might look similar, they are different buildings. The school has 3 levels with rectangular windows with a pyramid top while the building in the brochure only has 2 levels of non-rectangular windows and more of a dome shape on top.
Audio problem: In the scene "By The Throat", After Osmosis goes down the escalator. The red smoke starts to go around them. Osmosis moves his mouth with no sound, but not until a couple seconds later when the shot changes do you hear what is that cherry stench. (00:20:37)
Audio problem: When Drix and Osmosis investigate The Zit and Osmosis prompts him to "shake a tail cell" he smacks his rear but there is no sound effect.