'Key & Peele' BOMB at Comedy Festival ... Crowd Erupts in BOOS

Every comic bombs ... it's a right of passage ... and this weekend, the guys behind the hit Comedy Central show "Key & Peele" earned their suck stripes at a comedy show in NorCal.

The duo was performing at the Wild 94.9 Comedy Jam near San Francisco when the crowd turned on the comics during a bit about athletes with weird names ... and smothered Key & Peele in a chorus of boos.

After it was clear there was no winning back the crowd, one of the comics told the audience ... "thank you ... you guys are amazing ... couple of classy ones out there."

Kinda shocking ... 'cause we're told the comedy team usually KILLS IT on stage ... and recently impressed at a prestigious comedy festival in Montreal.

We called Key & Peele's rep for comment -- but the rep's assistant wouldn't put us through ... and told us they had no comment.