Invasion of the Ferb Snatcher/Ain't No Kiddie Ride - S2-E28
Character mistake: In 'Ain't No Kiddie Ride' Carl reminds Major Monogram that he has no sense of smell and that he was born without nostrils noting it on his resume. But in 'Brain Dead' when Major Monogram sees Perry wearing a face mask he points out that Carl is also a germaphobe. Carl corrects him saying "It's not the germs sir, it's the garlic smell." He wouldn't be able to smell anything since he has no nostrils. (01:10:00 - 01:35:00)
Burple Nurples/Shnitzel Makes a Deposit - S1-E2
Character mistake: In "Burple Nurples", Chowder was selling Burple Nurples for 5 dollops each. Later, Mung Daal steals a tray of six Burple Nurples, and Chowder runs after him, telling him that he owes him 300 dollops, instead of 30.
Suggested correction: The tray had more than 6, even if it was drawn to look like just 6, they could have been stacked on top of each other. Later when they're dumped in the fire, you can see more than 6 go in. Plus at that point we don't know how much Chowder was selling them for since it was after Mung Daal (while in disguise) paid more than 5 dollops for one.