This is taken from the movie Bill and Ted's Bogus journey. It refers to evil robot Ted and evil robot Bill seeing the photos of the princesess and Evil Ted getting a semi-erection and saying "I got a full-on robot chubby." Chubby being his penis before becoming turgid.
It has nothin to do with being turned on by robots. It is to do with ROBOTS being turned on!
Evil robotTed: I got a full on robot chubby.
Evil robot Bill: Excellent! (Probably!)