Green’s Dictionary of Slang

(a) (US black) a white person.

1971

H.E. Roberts Third Ear n.p.: mickey mouse n. a white man.

(b) (US) a small, silly or inconsequential person.

1935		S. Lewis It Can’t Happen Here 86: Dr. Goebbels. [...] is privily known throughout Germany as ‘Wotan’s Mickey Mouse’.
1941		S.F. Examiner 2 Mar. (Picture Rev. section) 7/1: George Graham, a timid, middle-aged mickey mouse who was afraid of crowds, people, anything [OED].
1968		‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 27: mickey mouse – Very square; jive melon farmer.
1973		A. Bennett Habeus Corpus Act I: Mad? You? You Mickey Mouse. Why don’t you marry someone your own size?
1979		E. Torres After Hours 179: These guys was no Mickey Mouse.

(c) (US black) one who plays commercialized music, esp. uninspired jazz music [Mickey Mouse adj.¹ (1)].

c.1940

Louis Jordan ‘Boogie Woogie Comes To Town’ 🎵 Don’t you be no Mickey Mouse, / If you can’t play no Boogie Woogie / Lock yourself in the barrelhouse.

(d) (US) a trivial, petty or unnecessary activity.

1958		J. Davis College Vocab. 13: Mickey mouse – An activity which has no purpose.
1969		H. Ellison ‘A Boy and his Dog’ in Beast that Shouted Love (1976) 190: Come on, forget the mickeymouse. What’s up?
1977		(con. 1969) M. Herr Dispatches 29: My last tour was better though, not so much mickeymouse.
1987		(con. 1967) E. Spencer Welcome to Vietnam (1989) 38: My job is [...] to keep the Marine Corps off their backs. [...] Fuck the mickey mouse.

(e) (US) foolish or nonsensical talk.

1980

‘John le Carré’ Smiley’s People 145: They make up some piece of mickey-mouse.

(a) (orig. theatre) a house.

[1960		J. Franklyn Dict. of Rhy. Sl. 96/1: Mickey Mouse House [...] Current in the theatrical world. The ‘House ’ is the theatre – the auditorium – the audience].
1971		J. Jones Rhy. Cockney Sl.
1978		Maledicta II:1+2 (Summer/Winter) 120: The Telegraph author [...] doesn’t seem to recognize the American origin of George Raft (‘draught’), Mickey Mouse (‘house’), Raquel Welch (‘belch’), and so on.
2001		M. Coles Bible in Cockney 28: You’re in charge of everything in my Mickey.

(b) a Liverpudlian [= Scouse n. (1)].

1992

R. Puxley Cockney Rabbit.

(a) a black and white police patrol car; also attrib.

1971		J.D. Horan Blue Messiah 54: The Mickey Mouse comes around and the cop puts out his hand. You pay or the bastards lock you up.
1971		S. Stevens Way Uptown 161: Two Mickey Mouse wagons are down the end of the block at Park Avenue, their blood-red eyes turning ’round and ’round.

(b) a police officer.

1971

E.E. Landy Underground Dict. (1972).