It's possible he shouldn't be regarded as a specific person, as another similar character is seen on the promotional flyers.
Mr. You! is a seemingly brave pilot, based on his involvement in the game. He is always seen smiling, which suggests that he not only enjoys his profession, but also the dangerous situation he has found himself in. Whether he likes to help out, or simply is foolish enough not to realize that he could be jeopardizing his life remains unknown.
Based on his in-game picture, Mr. You! appears to be a rather chubby man, possibly because of his very short legs. His proportions all seem to be a bit odd though, with a head about the size of his body and a long nose. Nonetheless he seems to be happy with his appearance, always having a smile on his face.
As a pilot, Mr. You is depicted with classic flight gear. He wears a flight cap with goggles and a flight suit, not unlike those worn by Japanese navy pilots during WWII.
InSky SkipperMr. You! sets out to save the royal family of the Wonder-Kingdom. It has been conquered by gorillas, and they have taken the king and his family captive. He arms his plane with bombs in preparation for his rescue attempt, ready to take on the gorillas. In battle, Mr. You! drops bombs on the apes, thus knocking them out. As the gorillas are recovering, he picks up the royalty they were watching. His opponents doesn't let him fly freely though, attempting to knock him out of the air by throwing bombs and trying to hit the plane, attacks which he carefully dodges.
All of the family is eventually rescued, and as the gorillas are caged, the others celebrate the victory.It's suggested that Mr. You! was sent out on the mission by someone else, as the game begins with a message, ending in "See you again at the airport."