Gary appeared taller than Belson, and fatter and has a brown mullet and yet a fatter face and cheeks that are similar to Clarence's and an unibrow similar to Belson's, and wears a black short-sleeve shirt and shorts, and medium gray socks and black shoes.
Gary Mooch is a rather Grumpy Kid with a rather mean spirited personality from turning off Belson's game to Stealing his Game Buddy 2. Gary uses Belson's Father as a way to get to him implying that he knows that he isn't around. However Gary isn't completely Hostile to Belson as he was willing to help Belson attack Clarence with snowballs during the snowstorm after Clarence accidentally breaks the GB2.
Belson and Gary Mooch are cousins, which both don't seem to each along with each other as Gary seems to take a bit of demand of being far worse that Belson itself, as both will likely fight it out against each other, until later in the episode when Clarence And Belson went to go find him, as once again started to fight it out until when Clarence rolled over Belson's video game, therby, destroying it, which both at the end, putting Clarence into a pile of snow where Gary was found and both throwing snowballs at Clarence and later left him there while both headed back to Belson's place.
The gallery for Gary Mooch can be found here.