The cuties joke really bothers me when it is obvious that Robot feels sympathy for Monster Girl from the beginning. Precisely because they both have the same problem that their exterior does not reflect how they both feel and they start from that sympathy to a relationship. Robot himself says that watching her fight despite her ability to count death inspires him to be better in Season 1. It is obvious that Rex is too smart to care about trivial things like gender or age. In this sense, Robot’s love for Monster Girl is one of the purest out there.