Sins of the Fathers Chapter 8: The Ultimate Slayer - S3-E8
Factual error: Despite being a paraplegic, when Smythe is about to be lowered into the vat of chemicals, his legs are pretty toned and muscular. The show implies that Smythe had been wheelchair-bound for a long time, so even if he had muscular legs prior to his paralysis, the muscles would have atrophied.
Enemy Within, Enemy Without - S1-E6
Continuity mistake: When Alana is grabbing the tree branch to break it off, her hands are suddenly closer together when the shot changes, and the branch itself has a different shape to it. (00:12:38)
The Origin of the Fantastic Four: Part 1 - S1-E1
Continuity mistake: When the Fantastic Four are first shown on Dick Clark's show, Johnny is seated on Sue's right and Reed is seated to her left. A couple of shots later when Dick Clark is telling them what his telethon viewers really want to know, Johnny and Reed have swapped sides. (00:02:06)