Michael Cera fits right in with the nerds

Celebrities are fairly regular sightings at SXSW, given that there's a film festival running alongside SXSW Interactive. But it's only recently that the geekier portion of the conference has attracted legitimate celebrities to its packed roster of panels and parties.

Actor Michael Cera ("Juno," "Arrested Development") stopped by a Sunday night party at The Mohawk, thrown by StumbleUpon and digital agency The Barbarian Group. He took part in an onstage jam in the process.

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Photo by: The Barbarian Group / Caption by:

Jake Gyllenhaal, professed Apple fanboy

"Brokeback Mountain" and "Donnie Darko" actor Jake Gyllenhaal stopped by SXSW to promote his new movie, "Source Code" (and he took some time to chat with CNET in the process about a promotional game running alongside its release).

Gyllenhaal's presence at SXSW also resulted in at least one gossip headline involving a rogue camera and a men's restroom.

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Photo by: Caroline McCarthy/CNET / Caption by:

Mike Tyson in the SXSW ring

Heavyweight boxing legend Mike Tyson was around to promote his new iPhone and iPad game, "Mike Tyson's Main Event." Here, he poses with the creators of the game.

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Photo by: Caroline McCarthy/CNET / Caption by:

Ashton holds court

Actor Ashton Kutcher was one of the few Hollywood types in town for reasons legitimately related to tech--he's one of the most prominent angel investors in the business , with a stake in companies like Foursquare, Hipmunk, and Fashism.

Kutcher co-sponsored a party at Hangar Lounge for several of his portfolio companies; his wife, actress Demi Moore, was also in attendance.

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Photo by: Caroline McCarthy/CNET / Caption by:

Twitter hero Conan O'Brien

Late-night TV host ( and Twitter hero ) Conan O'Brien was prowling around the SXSW scene, too.

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Photo by: Daniel Terdiman/CNET / Caption by:

A candid Pee-Wee Herman

Cult hero Pee-Wee Herman (in real life, comedian Paul Reubens), who has made the use of Twitter and Foursquare a big part of his recent revival in pop culture, appeared at several official and unofficial SXSW events and was surrounded by admiring (or amused) fans just about everywhere.

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Photo by: Daniel Terdiman/CNET / Caption by:

Dwight Schrute in the house

Actor and comedian Rainn Wilson (far left) was at SXSW mainly for its film festival, in order to promote his new movie. But he swung by the Interactive portion of the festival as well; here, he sits in for an interview conducted by Facebook at cable channel IFC's pop-up headquarters.
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Photo by: Aubrey Sabala / Caption by:
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