
Visible crew/equipment: In the scene when Kermit confronts Doc Hopper he comes walking out of the bar. If you look at the top of Kermit's legs when he walks out, two pair of hands can be seen moving the legs.

Visible crew/equipment: In the scene where Kermit meets Fozzie, when Fozzie tosses the rubber chicken over his shoulder you can see Frank Oz's arm and where the glove ends.
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.