The Secret Origin of Denzel Crocker - S3-E8
Factual error: Each time Timmy jumps through time, he goes back 10 years from 2002 (1992, 1982, 1972). However, some of the 80's references, such as Miami Vice, Flashdance & Back To the Future all came out after 1982.
A Case of Dairy-Uh / Lights, Camera, Adam - S3-E13
Factual error: The man that Vicky has a crush on (or something like that) drinks his tea, but the level doesn't go down.
The Big Scoop / Pipe Down - S3-E10
Factual error: After Timmy makes his wish of having no sound, and he finally wakes up, the clock said 7:42 (before we see Timmy waking up), but when he walks there, it read 7:43, then jumped to 7:44 on the same shot.