Plot hole: In the episode where Joey tells Jimmy that Michael is his son and they cut of some of his hair to do a DNA test, Gina tells Michael that he is missing some hair on the back of his head. In the next shot the angle changes, we can now see the back of Michael's head, and he's not missing any hair.
Plot hole: The Mad Scientist's lair is on the top of a tall pointy mountain with no real flat areas. But Lois is somehow able to land her 1930's-1940's era propeller plane on the top of this mountain with no runways or flats for her to come to a stop on from flying. Which is physically impossible. (00:04:45)