Justin Bieber's Got Yer Footlong Right Here

Justin Bieber is one helluva a multitasker ... dancing, chowing down on a sub and getting some QT with Sofia Richie ... and he did it all in front of the TMZ Celebrity Tour bus.

Sofia and the Biebs were cruising down Sunset Blvd in WeHo Thursday during rush hour when they ended up stopped next to our bus.

We tried to get some intel on JB's sandwich of choice, but all he was giving up was his dance moves. Fans on the bus and on Sunset Blvd. seemed more than satisfied.