Gary is the tritagonist in the 2011 feature film, The Muppets. He is played by Jason Segel.
He is the brother of a Muppet-like humanoid named Walter and is dating Mary (played by Amy Adams).
Like his brother, Gary is a huge Muppet fan and, together, they set out to reunite the Muppets to help save the Muppet Studios from destruction.
According to an interview with Walter and Kermit, Walter actually has three brothers and that "Gary" was just a character created for the movie.
A stand-in extra makes a cameo as Gary in the sequel Muppets Most Wanted, with his back at the camera.