I have no idea whether this footage is genuine or a viral campaign for Grand Theft Auto V – a TV-news report suggests it's real – but the central fact remains: An anonymous thrill-seeker got on a Motocross-style dirtbike and took it on a tear through the Russian subway. And some gentleman even politely opened a station door so he could do it.
Russia's metro system can be a circus of the surreal, with feral dogs hopping trains, horribly bloody police brawls, doors that stay open mid-tunnel, and (possibly NSFW) amorous hookups that put the "public" in public transit. So this man's bumpy journey down the stairs, along the platform, and back up the stairs into the streets blends right in with the subway's more bizarre incidents. The two-wheeled intruder even wore a helmet during the trek because, you know, safety first when using a mass-transit station like your own backyard racetrack.
Some earlier versions of this video feature just the engine noise and distressed cries of one bystander; the above clip adds David Bowie's necessary rock anthem, "Rebel Rebel." If anybody speaks the language, here's a Russian-media interview that contains a bit more footage from the nutty ride (and a wheelie away from the scene of the crime):