Montreal's annual Osheaga Music Festival went down this past weekend, and as always with these major music events, there were several surprises. Mos Def joined Kendrick Lamar on stage to perform Lamar's "Alright," a collaboration that left Lamar star-struck, considering Yasiin Bey has been one of the rapper's all-time idols.

Another surprise involved Weezer's Aug. 1 set, where frontman Rivers Cuomo brought out his two young kids to perform a couple of tracks with the band.

Cuomo's adorable three-year-old son Leo nailed some flawless inflatable guitar riffs for "Back to the Shack," sporting ear protection, of course. His 12-year-old daughter Mia manned the keys for "Perfect Situation." You can check out some fan-captured images of the young aspiring musicians below:

Weezer will take a quick break from the stage until early September for a short festival circuit; they are scheduled to appear at Riot Fest as well as a few other events. You can stay up-to-date with the band and their itinerary over at their official website.

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