We really wanted to make a Squaredy Cat *pop* off a bright pink heart, so we associated it with the phrase, "not squared to XOXO." The phrase is pretty open-ended. It means hug and kiss, but it can be a romantic smooch or a friendly peck; a warm, loving embrace or a passionate cuddle.
Maybe XO also looks like an *ouchie* emoticon. We hope it doesn't hurt you to love :)