Fallon sings "Start Me Up" by the Rolling Stones at Billy Joel MSG concert Thursday night.
Credit: Suarez/WireImage

Billy Joel and Jimmy Fallon were in a “New York State of Mind” Thursday night.

Joel, 67, appeared on The Tonight Show Wednesday and suggested bringing longtime pal Fallon, 41, on stage during his performance at Madison Square Garden the next night.

“You coming? So we’ll do something on stage,” Joel suggested.

An offer Fallon couldn’t refuse.

Come Thursday, Fallon made his way up mid show and the duo sang the Rolling Stone’s Start Me Up before breaking into several doo-wop numbers, reminiscent of their impromptu jam session earlier in the week.

The pair was such a hit that Fallon joined Joel once again for the show’s encore.