Oh, My Aching Antenna - S1-E33
Continuity mistake: Even though Tim and Uncle Martin live on the 2nd floor at Mrs. Brown's above the garage, every view outside the living room window with the sheer drapes shows the house across the street from a ground floor perspective. This happens in multiple episodes.
Continuity mistake: The fireplace moves from episode to episode, from the center of the room to the corner.
When You Get Back to Mars, Are You Going to Get It - S3-E24
Visible crew/equipment: When Tim and Martin are carrying Andromeda to the bedroom and Martin opens the door with his Martian finger, the crewmember actually opening the door can be seen on the hinged side of the door. The crewmember continues to move in that space for about 3 seconds during the scene. (00:10:00)
Uncle Martin: We don't have love at first sight on Mars. Either it was too silly to bother with, or it was something we discarded in our Dusk Ages.
Tim O'Hara: You mean the Dark Ages?
Uncle Martin: We were never that primitive.