A ratchety individual who is so obnoxious said person seems not human. Someone who is over the top, projecting a mentality at a volume or with movements to get attention. This can be a demeanor thing or aesthetic thing. Like being a puppet, puppets aren't real there for, a muppet is being fake going along with things just to fit in.
(A bunch of teenage girls yelling and giggling over irrelevant things in public) one would say, "Look at those jankey ass "Muppets"!
"Look at her her blue eye shadow someone felt Muppety today."
(Wearing a shirt where you can see the bra clearly through it) "What a "Muppet."
"Whats the difference between a "Muppet" and a regular girl? Daddy issues."