M&M is Cathy Carlson's 13 year old brother in S.E. Hinton's teen novel That Was Then, This Is Now. M&M gets his nickname from his love of the candy of the same name. Unlike Bryon and Mark, M&M is a young hippie: He has long hair and wears an old army jacket with a peace symbol hanging from his neck. He seems to be popular with just about everyone except his father, who nags him relentlessly about his bad grades. Bryon particularly likes M&M because Bryon is interested in M&M's sister, Cathy. M&M likes smoking pot, and he eventually runs away from home, ending up in a "hippie house," where he is given another nickname, "Baby Freak." He eventually turns to LSD. Bryon and Cathy finally locate him at the house, where he is suffering from a particular bad trip in which spiders have been eating at him. The bad trip has a lasting effect on M&M: His grades have gotten worse and he has memory lapses.