Visible crew/equipment: When Kel gets up to get more water you can see one of the cameras.
Continuity mistake: Ray places a donut that Debra throws at him on the third step and then stands up. Later the donut appears on the second step when Frank comes down the stairs. (00:19:15 - 00:20:45)
Not in the Line of Fire - S3-E15
Continuity mistake: When the vendor throws the hotdog at the press conference, a lot of the toppings/condiments trail behind it. When the shot changes and the hotdog hits Mike, there are no condiments trailing behind it. (00:19:10)
Weird Cousin / Baby Oskar - S4-E11
Factual error: Stephen Viksten is credited twice for voicing Oskar.
Continuity mistake: The bottle of orange soda on the breakfast tray Dick tries to bring to Mary changes to a bottle of alcohol (Jack Daniel's I believe) when he sets it down. It later changes back into the bottle of orange soda.
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.
First Kiss - S1-E17
Visible crew/equipment: At the end of the episode when Harvey hops away, a boom mic is visible. (00:21:55)
Midori no chikyû wa makasetoke - S1-E2
Other mistake: When Yurika restarts the Nadesico, one of the screens pop up with a huge congratulatory "SAFATY ROCK OFF." (00:18:05)