-Flowey and Dimentio Affably evil asshole that everybody loves to hate. Although they don't seem more than a nuisance for much of the game, in the end they become an abomination of a final boss. They possess the same unusual reality-warping powers of the main character, which otherwise are quite hyped up and centralized around this player character. They take one or multiple heart-shaped magical objects (as well as power from well-loved characters) from the previously described character, that are very powerful, in order to destroy existence. Their main final battle has them functionally invincible until multiple colourful heart objects circle around the player character, after which this defense is dropped and the battle can be won. Many consider their battle themes incomplete without the sound effects from their bullet hell of a boss fight.

-Alphys and Francis One of the most obvious ones. Nerdy lizard who absolutely loves anime. Super girly anime. And cats. They get very noticeably nervous around those they have a crush on (but are kind of nervous in general anyways). Both impede the player quite a bit, in fact. Are known for complaining about the sequels to their favorite anime. Both simulate a date with the player (in which they consider giving items to boost a made up dating statistic) but fail very easily out of nervousness. They even resemble each other even taking into account that they're both lizard furries. Same posture and back of head spikes (that not all lizards have.) Both build robots that also impede the player's progress and are in some cases invincible because of sturdy metal plating.

-Muffet and Mimi Girly, pigtailed spider girl who wants your money- and a lot of it. In the battle with her you are chased by a rather scary spider type thing.