Despite what its name seems to claim, Ben Folds Five was a trio—not a quintet—made up of Ben Folds, Darren Jessee, and Robert Sledge.
John Flansburgh directed the video for their song "Song for the Dumped." Apparently John hung out with Robert, who convinced him to do the video. In addition, both Mark Feldman and Frank London, session musicians for TMBG, provide violin and trumpet on Ben Folds Five's final album, 1999's The Unauthorized Biography of Reinhold Messner.
More recently, Darren Jessee's new band, Hotel Lights, covered the TMBG song The End Of The Tour on Hello Radio: The Songs Of They Might Be Giants.