When Avatar is telling the president about his brother, the narrator says that Blackwolf has been studying black magic for 5,000 years. But when Blackwolf is introduced, it says that the story takes place 3,000 years later.
Just before Avatar's party sets off toward Scortch, the narrator tells us that Elinore visits her village to "say goodbye to her father," etc. But her father--the president--is already dead (to wit, murdered by the robot assassin), as Elinore herself tells us moments later. Actually, this is not a goof. In the illustration accompanying this narration, Elinore is shown kneeling in front of her father's tomb in prayer. This is what was meant by "saying goodbye to her father."
During the chase scene with Necron 99, a quiver suddenly appears on Weehawk's back between shots.
The narrator says that after the initial nuclear apocalypse, "It took two million years for the clouds to disperse." This would be more than enough time for the nuclear material to decay to harmless levels, assuming that "dirtier" bombs had not been created prior to the apocalypse.
The swastika in Blackwolf's chamber bends to the left, which is of Hindu origin, a ward against evil. Nazi swastikas bend to the right.
Avatar transforms his pet into a jukebox which immediately begins to play jazz. But the record is still on the selector arm, and remains there. It never actually drops onto the turntable. However, the jukebox is magical in origin so this shouldn't be surprising.
Mark Hamill's name is misspelled in the credit sequence as "Mark Hamil"
Avatar says, "I searched for my brother in vain," but then says that Blackwolf settled in the land of Scortch. If Avatar knew that, then his search was not in vain at all.
Just before the battle of East Elfland, the fairy leader is addressing her troops, but she mistakenly calls the enemy leader Black Mark.
After receiving the news about the assassinations of the heads of his neighboring states, Blackwolf declares that the successors will blame the deaths on people in their own ranks. But Blackwolf is the only ruler who still uses technology, and his assassins are armed with automatic rifles. Blackwolf will immediately be blamed.