Manny is Greg's obnoxious little brother. He is always doing bad things that Greg gets in trouble for. In the movie he states that he is "Onwy Thwee" as an excuse for what he did.
Manny is a huge tattle tale. He told on Greg for something he did a two years ago before Many could even talk. If you look past his cuteness he is a very devious child and always getting Greg into trouble. His parents are blindsided by his cuteness and dont beleive Greg when he tells on Manny. He acts immature even for his age. He wouldn't give up his shreded blanket "Tingy" and when it got thrown out he fished it out of the trash and hugged it while it was still covered in trash. He is also very selfish but only Greg and Rodrick see past his disguise.
His hobby is being a nuisance to everyone around him. In Cabin Fever turned off all of the heat in his house except in his room and stayed there while his family froze. He also won't eat anything that comes his way. He also likes to watch T.V.