Green’s Dictionary of Slang

1. a child, a small person.

1999

Guardian Guide 21–27 Aug. 28: Proletarian shed music – ‘playground techno’ [...] was for ‘muppets’.

2. a police officer or magistrate.

1989

J. Morton Lowspeak 102: Muppet – 1. a uniformed policeman. 2. a lay magistrate.

3. an unattractive person, a fool, poss. one who is mentally retarded; a term of abuse.

1997		‘Q’ Deadmeat 53: I thought you’d be dead by now, you muppet.
2004		(con. 1990s) N. ‘Razor’ Smith A Few Kind Words and a Loaded Gun 436: Here I was [...] being verbally abused by some two-bob muppet.
2006		Observer Mag. 15 Jan. 14/2: New forensic evidence [...] will show that the two hit-men – ‘those muppets’ – were wrongly convicted.
2012		(con. 1980s) I. Welsh Skagboys 257: Runnin up ma fuckin phone bill, ya muppet!
2015		I. Welsh Decent Ride 30: Laughin as the fuckin muppets shout and swear eftir ye.
2018		G. Gilmore Base Nature [ebook] ‘Bleeding hell, you muppet!’.

4. an assistant.

2008

J. Niven Kill Your Friends (2009) 37: ‘Gunter.’ he nods to his muppet who hits ‘play’ on the DAT machine.