If you thought the Eminem / Jay-Z stadium pair-up was astounding, you should've seen Drake's OVO Festival.

The Young Money signee announced he'd be headlining his own Toronto-based, day-long music fest last month, with other announced performers including Francis & the Lights, Young Jeezy and Bun B.

It was the unannounced guests that stole the sold-out show last night (Aug. 1), however. Jay-Z, Eminem, Rick Ross, Young Jeezy and Fabolous all took part in Drake's set at the Molson Amphitheater. Eminem, whom Drake called "the greatest of all time," helped out on "Forever," while Jay-Z ("My man who's inspired me more than anybody in my motherf*cking life") came on for his own "Run this Town."

"I want to bring somebody to the stage. I want to pay homage to a legendary rap group, a dude that came out here to perform for y'all," Drake said introducing Bun B -- formerly of UGK, now touting his solo effort "Trill OG" (due tomorrow).

Ross performed "B.M.F.," Fabolous was on "Throw It in the Bag," Jeezy rapped on "Unforgettable" and Kardinal Offishall had "Ol Time Killin'."

OVO shined off Drakes national tour in support of his album "Thank Me Later." Videos, courtesy of Rap Radar, below.