Revealing mistake: Season 4, episode 5 "Ben 4 Good Buddy": When the Baron drives off from the garage in the Rust Bucket, the VR's interior shifts unnaturally; an obvious glitch in the computer animation.
Ben 10 (2005)
1 revealing mistake in show generally
Starring: Tara Strong, Dee Bradley Baker, Paul Eiding, Meagan Smith
The Krakken - S1-E3
Continuity mistake: When The Krakken snatches the Cannery crate from the boat, you can see that the lower horizontal bar from the 'E' is suddenly missing, thus reading 'Cannfry'.
Grandpa Max Tennyson: Being a hero isn't about letting others know you did the right thing, it's about you knowing you did the right thing.
Ben Tennyson: What were you just doing, reading greeting cards back at the Mega Mart?
Grandpa Max Tennyson: Well... yes.
Trivia: 4-9 "Ben 10 vs The Negative 10 I": The holiday camp where Cooper is picked up by Max Tennyson looks quite like Camp Opinicon from season 2's "Camp Fear".