In the 2009 hit movie 'I Love You, Man,' Paul Rudd and Jason Segel play buddies who bond over a shared love of the holy triumvirate known as Rush (the guys jam to the band's songs, and Rush themselves appeared in the movie during a concert scene). Later on, Rudd and Segel reprised their roles alongside the band members in a Funny or Die video that closed the shows on Rush's 2010-11 Time Machine Tour.

So really, no one should've been surprised to see Paul Rudd on stage with the group as they wrapped up their Clockwork Angels Tour. On Aug. 4, Rush was in Kansas City playing the last show of the nearly year-long tour when audience members at the Sprint Center noticed something strange.

"Towards the end, the last song the string section played in ('YYZ' I think), a man came out on stage and was standing behind Neil directing the string section like a composer," wrote a poster on the Rush Forum. "After a bit he turned around and ... it was Paul Rudd!"

"Alex and Geddy both came over to the riser and shook Paul's hand, and Neil got up from his kit and extended his hand out to shake his hand as well," another fan wrote. "Geddy not only thanked the string ensemble but he thanked Paul Rudd by name, which got a nice response."

As you'll see in the video, Paul gamely played along, even doing his dorky "slappin da bass" move -- up high where it belongs, of course.