Continuity mistake: When Malcolm is trying to get the TV back to the channel he was watching, he picks up a big remote and finds the channel which the video camera feed is on, but the remote he is holding on the TV is a smaller one. It then cuts back to Malcolm who is moving his hand away from the remote he just put down and it's the bigger one again.
Visible crew/equipment: When Dewey yells for Lois because the bow was put on the present, if you look to the left of Lois, you will see a crewmember kneeling down, handing Lois the Red Dress, who is holding a bucket of water. He quickly gets out of the camera's view. [This is on the DVD of the first season. Someone said on the audio commentary that after catching it, they deliberately left it in to see if anyone would spot it. It's still a mistake, but that's why it's there.]
Opening theme song: Yes, no, maybe, I don't know, can you repeat the question? You're not the boss of me now, You're not the boss of me now, You're not the boss of me now, and you're not so big. You're not the boss of me now, You're not the boss of me now, You're not the boss of me now, and you're not so big. Life is unfair.