Princess Irmaplotz is the evil sorceress princess of Hyrogoth that is trying to destroy Dave the Barbarian (or more likely she just wants to make Dave's life miserable). Her mother Queen Zonthara is the ruler of Hyrogoth, and keeps on trying to teach Irmaplotz to be more evil. Her father is good, making her half-evil. Earlier in the show, Dave and Irmaplotz fell in love, but Dave decided that they were too different, and ended up dumping her, where she is now seeking revenge. She still may have feelings for him though; she once got the chance to destroy Dave, but she chose not to do so. She is similar to Dave in that they both have the same odd hobbies and interests (she and Dave both love "bad poetry" for example). She also has the same allergies as Dave. She is very beautiful and an intellectual; she would be a great match for Dave, only if she were not an evil princess. She occasionally wears glasses (she has stated that she does not like to wear them as she feels they make her look bookish, even though she cannot see things from far away without them), due to her being nearsighted.
Dave and Irmaplotz's relationship is similar to that of Anna and Hans in Frozen (Irmaplotz sought revenge on Dave [to take over his castle] after he dumped her, while Hans pretended to like Anna to take over her kingdom and kill Elsa so he could be king).