The singer and chat show host are competing to be Justin's best friend!
Shawn was appearing on Jimmy's programme when they got to talking about JT, with whom Shawn recently performed at the iHeartRadio Awards.
Jimmy and Justin have been friends for a while...
...so Jimmy ended up getting into a joke spat with the Canadian singer about which one of them Justin prefers!
Cover image via The Tonight Show Starring Jimmy Fallon/YouTube