Regarding Sweetums

[theprawncracker]

I believe he was a marionette.

I think the Muppeteers were in trees and they manuevered his legs to make it look like he was riding the bike.

Hope this is right, and it helps.

 

[DMETxix]

Regarding Sweetums and similar puppets:
This recent thread talks about it.
(Check out Jinx and Buck-Beaver's reply.)

Regarding the Muppets riding bikes:
Check out Fish'N'Wolfe's reply on this thread.

 

[BEAR]

Hey, I would like to discuss Sweetums' character for a minute. Notice how in just about everything he is in, he first comes off as a scary bad guy, but then in the end it turns out that he is really sweet and helps them in the end. Maybe that is why he is called Sweetums!!