Jimmy Fallon was joined by some “Saturday Night Live” buddies on “The Tonight Show” Monday night for a hilarious sing-a-long.

The boys from The Lonely Island, which includes Andy Samberg, Jorma Taccone and Akiva Schaffer, broke out some old-school classroom instruments to jam out with Fallon and The Roots in a TV-friendly rendition of one of their most notable hits, “I’m On A Boat.”

The Lonely Island boys were on the show to promote their new film “Popstar: Never Stop Never Stopping.”

The movie is set to hit theaters on June 3.