One of the Madmen who serves as a supporting player in Karl's story, Squid ended up in the group because "something awful happened to him, we don't want to think about it, put him in counseling" (3.85). Specifically, his dad went to prison, started corresponding with a hillbilly chick, then divorced Squid's mom and married Hot Hillbilly Girl when he got out.
That's bad enough on its own, but Squid's dad pushed it further by calling and writing to his ex-wife and belittling her, telling her how much better Hot Hillbilly Girl was than her. Eventually, Squid's mom killed herself. Left in the custody of their father and stepmother, Squid and his younger siblings are the targets of abuse. "I'd seen the marks on Squid's back in the gym class showers" (3.88), Karl says.
Karl and Squid also have a complex relationship because after his father's death, Karl killed Squid's pet rabbit. While this created distance between them, the mutual deaths of their parents, as well as Karl protecting Squid from assaults of questions in therapy and bullying, made them friends. "I couldn't stand to think about how lonely the guy was feeling," Karl says. "I wanted to be a friend for him worse than I'd ever wanted anything" (4.61). Since then, Squid and Karl have been friends, fellow Madmen, and have had each other's back. Go team.