A while back, I asked if Watterson ever did squid. I was informed by Philip Johnson (no, not that Phillip Johnson—this is the one who has not dedicated the declining years of his life to stupidity and evil) that a marvelous thing exists…The Calvin and Hobbes searchable database. You can search an archive of Calvin & Hobbes cartoons by keyword! Sometimes I do love the internets.
He does reference squid a few times (Calvin has a squid eyeball sandwich one day, for instance), but he doesn’t draw them. There are two cartoons with Calvin as an octopus, though.