Sammo Blammo - S2-E1
Continuity mistake: In the scene at the bank, he has a bomb attached to him and an ex-bad guy handcuffed next to him, the handcuff is roughly a foot long, making the distance short between him and the guy next to him. Sammo fights a gang of thugs in the bank and does a swing round kick and his handcuff is detached or widens by 3-4 ft. The guy on the floor is rolling around to make it look like he is attached to Sammo, but is clearly not.
Plot hole: During the episode "Superstition", Onizuka thinks he has cancer because the magnetic pain-pads he was wearing created strange blobs in the X-Ray he has taken. However, given the fact that the X-Ray was so strange, doctors would have given him a complete physical, and noticed the pads much sooner. Here, they literally just assume he has tumors, and fail to ever take notice of the pads. Simply impossible, given the gravity of the situation. (Obviously, this is to pay off at the very end of the episode.)
The Planet of Dr. Moreau - S1-E4
Other mistake: When the mountain starts to collapse, the Silver Surfer and the enslaved trolls begin falling to the ground below at a rate comparable to what the falling rate on Earth would be. The Surfer is able to catch himself on a ledge and absorb his restraining collar into himself, granting him control over his powers, which he uses to prevent the trolls from falling to their deaths. With the amount of time the Surfer spent struggling to overcome his restraining collar, the trolls would have already fallen to the ground.
Continuity mistake: In the episode "Fool's Gold" Debbie puts the fool's gold on top of the pail on her sculpture. The shot changes and it's gone, the next shot it's back.
Character mistake: When the gang is watering the horses, Chris walks over to meet Mary's man friend (whom she introduces as an old friend of the family) and the mystery man tells Chris that he'd proposed to Mary long before 'Frank' when Mary's late husband was Steve.
Visible crew/equipment: In the opening sequence, when Karl opens the door to his apartment, you can see the top of the set wall and the stage lights hanging above, in the corner of his living room.