Other mistake: Whenever Fozzie is driving the Studebaker, the movements of the car don't correspond to the way he moves the steering wheel (he tends to crank it back and forth a lot).
Other mistake: In the fight scene right after Miss Piggy blasts the man through the wall, she kicks another man. If you look closely, he goes back from the kick a little, then just stands there and adjusts his hat.
Other mistake: As Fozzie corrects the car to keep from crashing, watch the two of them in the long shot by the church. They are bouncing very rapidly as they come to a stop, suggesting the film was sped up. Also, Fozzie looks to the left of the steering wheel to shift gears, rather than the right, where the shifter would be, on the transmission hump.
Other mistake: When Fozzie backs his car into Hopper's and then leaves, the front of the Caddy shows no damage, despite the severity of the hit. Not even a speck of paint on the bumper.
Answer: The closest thing to an answer is here, Martin Becker's obituary. His family states that it was a robotic Kermit on a bicycle. Outside of that, everyone else associated with the movie has been quiet on the subject.http://www.fridaythe13thfilms.com/saga/part5/martinbecker.html.
Rlvlk
They used gyros in the wheels - Martin Becker made the first self-driving bike for that movie-now the same tech is used in the self-driving bikes seen in the Netherlands. -Diana Becker, Martin's widow.