What Does Blue Want to Build? - S2-E2
Revealing mistake: When Mailbox first comes in, you can see the letter being moved into place behind Mailbox due to a small part of him being cut off. (00:13:00)
Blue's Clues (1996)
1 revealing mistake in What Does Blue Want to Build?
Starring: Aleisha Allen, Steve Burns, Seth O'Hickory, Traci Paige Johnson
Blue Wants to Play a Game - S1-E12
Other mistake: The jigsaw puzzle Steve and Blue help Shovel and Pail with has a picture of everyone playing musical chairs from the Mailbox's Birthday episode, but Steve suddenly isn't in the puzzle. He played musical chairs, so he should've been in the puzzle.
More trivia for Blue's Clues