wingnut, n.² — Green’s Dictionary of Slang

wingnut n.²

[SE wingnut, i.e. the shape, with its two protruding ‘ears’]

(Aus./UK juv.) a person with large, protruding ears.

[1982		N. Keesing Lily on the Dustbin 176: Protruding ears resemble ‘a head like a wing nut’ or ‘a Morris Minor [car] with the doors open’].
1988		L. Johansen Dinkum Dict. 467/1: wingnuts ears - especially protruding ones.
1998		S. Maloney Brish-off 18: [T]hey called them jug ears. Chrome - plated , his head wouldn't have looked out of place in a trophy cabinet. Wing Nut would have been a better nickname.
2001		OnLine Dict. of Playground Sl. 🌐 wingnut n. Someone with excessively large or protruding ears (e.g. Prince Charles).
2001		Chaser (Sydney) 12 Apr. 5/4: Queen: And my other lad is a jug-eared wing-nut.
2012		P. Corris Mad Dog [ebook] He covers them with his hands and feels them; how often has he heard comments about his ears? His ‘jug ears’, his ‘wing nuts’.
2017		T. Spicer Good Girl Stripped Bare 10: The Spicer legacy [...] is the wingnut [...] a person with protruding ears.