prick up one's ears and listen; listen attentively
Idiomatic expression from the Disney movie Dumbo, describing someone suddenly becoming very attentive and listening carefully. Often used with 〜になる.
When it came to her story, he suddenly pricked up his ears and listened.
I immediately prick up my ears when it comes to gossip.
From the Disney movie Dumbo, referring to the elephant's large ears, used figuratively for listening attentively.