looney tune, adj. — Green’s Dictionary of Slang

looney tune adj.

also loony-tune, loony-tunes

insane, irrational.

1971		L. Bangs in Psychotic Reactions (1988) 12: The whole musical world is packed with simpletons and charlatans, with a few a genius or looney tune joker in between.
1975		N. De Mille Smack Man (1991) 113: You got to watch out for the loony-toon hookers.
1984		S. King Thinner (1986) 93: ‘There is something,’ Billy said. ‘ Although it sounds a little Loony Tunes.’.
1993		R. Shell Iced 172: I didn’t want to hear no more shit about leprechauns and devils. The boy was clearly loony-tunes.
2000		J.J. Connolly Layer Cake 77: I’m thinking its gotta be one of the loony-tune soldiers from one of the barracks.

looney tunes palace (n.)

(N.Z. prison) cells used for unbalanced or possibly suicidal inmates.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 110/1: looney tunes palace n. cells mentally unbalanced or potentially suicidal inmates.