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.
Answer: It's a joke. One cannot list all forms of entertainment. The list would never end. The boys were trying to convey how superior they were to the others, by saying that they were too good for comedy.