Solid Snake is a recurring bit character in Sgt Frog Abridged. He will randomly pop his head in from off-screen to reference the Metal Gear Solid series, usually under the guise of it being advice. It is revealed in Episode 7 that this is apparently his job: he sits in front of a computer in a cave in the far-off planet Doinaka, waiting for someone to make a mistake. He will then teleport to their location to say something before immediately disappearing again.
So far only Fuyuki and Dororo are aware of his presence, though due to the retconning of the original Episode 2, it remains to be seen if Fuyuki will remain on that list.
Viper: *Fires his arm cannon* "Okay, how the fuck did I miss a picture?!" Snake: "Plug into the second controller port!" - Episode 4
Momoka: "Beautiful, isn't it? It just grew here all of a sudden a few weeks back. I don't even know where it came from." Paul: "I was just fixing my socks. I didn't think that would happen!" Snake: "Even love can bloom on the battlefield!" Dororo: "Shut up!" - Episode 10