When Jack is asking Isabel out on a date as they're standing by their trailers, he's very excited and walking backwards towards his trailer. His bicycle is behind him and it looks like he's just about to trip over it. When the camera cuts back to him, he's closer his trailer door and hasn't fallen over the bicycle, but it's not visible behind him anymore either.
After Isabel tells Jacks that she's a witch, he asks, "Am I gonna get pregnant? Because I cannot get pregnant right now." Endora cast a spell causing Darrin to feel the same pregnancy symptoms that Samantha was feeling in an early episode of the original series, "Bewitched".