Easter bunny, n.² — Green’s Dictionary of Slang

Easter bunny n.²

[the Easter bunny is a beneficent creature]

(US campus) a benefactor, someone who does a favour.

1991		Eble Campus Sl. Fall.
1996		Eble Sl. and Sociability 71: Easter bunny for ‘a benefactor, someone who does a favor’ mimics a 1991 M&M candy commercial.