Continuity mistake: Joey states he has never lived alone. Yet in "Friends," he had his own appartment.
Other mistake: In season one when Alex got divorced, Joey and Gina talked about how Gina got divorced from Michael's father while she was still in high school. In season two, we learn that Jimmy is Michael's father. Joey didn't even know that they were together, he certainly would have known if they were married.
Other mistake: How on earth can a jobbing actor in a late-night soap with a non-paying tenant afford a huge, luxurious, two-bedroom apartment, complete with balcony and communal hot-tub, all within a few miles of the Hollywood sign? That's the expensive side of L.A, and he'd be very lucky to get that apartment for under five figures a month.
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.
