Other mistake: According to "Attack of the Twonkies", if music is played around them, they'll mutate into a monster. However, in "My Big Fat Spy" during the song "I Have The Ring", there is a twonkie in the room that is somehow unaffected by the music.
Crouching Jimmy, Hidden Sheen - S3-E8
Other mistake: When Sheen is about to fight Yoo Yee, Jimmy puts the kung-fu disk in the dance machine. During the break in the fight, Jimmy asks Cark to get him the kung-fu disk to put in the dance machine, but Jimmy already had it in there at the start of the fight.
Other mistake: After Cindy says yes to Jimmy's proposal, he jumps with excitement until he realises what he did and screams "no" very loudly. Cindy is walking several feet away. How did she not hear him?