A type of puppet popularised by Sesame Street and The Muppet Show, typically operated with one hand of the puppeteer inside the head and a rod to move one arm of the puppet
Sally is such a muppet, the way she always gets George coffee.
(Brit. informal) an incompetent or foolish person. 1990s: from Muppet, the generic name given to various puppets and marionettes created for the children's television programmes Sesame Street and The Muppet Show