How bad is it? It's low budget and the cast seems to know they're in trash.
Should you see it? Yeah. It's a minor campfest.
Denise Richards in her first starring role plays a high school girl, whose boyfriend gets killed. Mad scientist Terry Kiser puts the boy's brain in an animatronic T. Rex. That leads to some romantic difficulties, as you might imagine. The lizard then goes on to get revenge on its tormentors in ways that seem violent at first and then become cartoonish. The T. Rex gets filled full of bullets, they plan to put the brain back in the original body (now rife with maggots and rats) and he ends up as a brain in a vat. It's so stupid that it's kind of enjoyable.