Boys in the Band / Hex Games - S2-E2
Deliberate mistake: When AJ and Chester show Timmy "The Timmy Tuck", AJ says it has a 1400 degree turn. The diagram shows 140°.
Mighty Mom and Dyno Dad / Knighty Knight - S2-E9
Deliberate mistake: Timmy's eyebrows show through his armor.
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.