I had the following revelation

Just out of nowhere it popped into my head: Kermit the frog must have been riding fixed gear in that scene in the first Muppet Movie where he's biking through the park (damn you youtube for not having it). That way the pedals would keep going and his feet would go up and down with them, so it would look like he was pedalling, even though he is not an alive animal but a puppet.

Figure 12: This bike is unusual

Of course this is the internet and so like 1000 people have already had this same revelation.