Really like this, and makes for a much-needed breath of fresh air compared to the stiff cut-out Flash type animation that most people tend to do nowadays. So much life in this.
If I do have comments, it would be the technical execution of the video quality, colour grading, and the keying:
- the overall colour looks faded and desaturated. Now you have triplets - with some small changes you will have three more distinct puppets ( which are still based on the same puppet).
Also, it would be interesting to have different eye expressions, depending on the mood of the character.
- the keying is pretty bad, and it results in obvious fringes and halos - definitely needs improvements.
- the all-caps subtitles don't really work that well. The faded gray is relatively hard to read. Check how regular TV formats these.
I feel you've faded the muppet parts because you wanted an old-fashioned look, but it doesn't really work: it now looks as if this is a 80s NTSC VHS recorded and converted video - I would just keep it sharp and saturated.
Otherwise, nice work. I also like the cutting, and compositing of multiple instances of the same characters. Perhaps consider changing the eyes of the same characters a bit that you clone into the scenes in order to give them more personal character.
What camera setup are you using?