Mainstream - S3-E3
Continuity mistake: When Kitty goes to get a midnight snack, her hair is down. But a few shots later, her hair is up in a ponytail.
Art Attack - S1-E12
Continuity mistake: The captain enters his quarters and leaves the door open behind him. When Max grabs the painting to leave the door is closed. She wouldn't have shut it because she was escaping immediately. (00:33:40)
Continuity mistake: The establishing shot of the Agency's headquarters building zooms in on 3 tall, narrow windows recessed into a brick wall. We then cut to an interior view - of several wide, continuous windows without any recesses. They don't match the exterior windows at all. (00:07:30)
Fear Burns Down to Ashes - S4-E15
Continuity mistake: Rev Bem returns for this episode, however the costume department seems to have forgotten all the changes his character went through in S3 "What Happens to a Rev Deferred?" His face is distinctly more Magog than it should be, and his hands have reverted back into clawed fingers.