HEY, PUNK!!! GET OUT OF THE ROAD!!!
YOU'RE BLOCKIN' TRAFFIC!!!!
... Oh, wait, it's just Asgore's kid.
Undyne shouting at Kris
Undyne is an anthropomorphic blue-skinned, fish-like monster with a long, red ponytail, fin-like appendages on the sides of her head, and jagged yellow teeth. She wears a navy blue police uniform, complete with navy blue tints. Unlike her counterpart in Undertale, who wears a black eye-patch over her left eye, Chief Undyne appears to have both eyes fully intact.
Undyne is hot-blooded and enthusiastic, and shows passion in everything she does, including things she does badly, such as singing. Her passionate nature leads her to overreact to minor incidents and she becomes easily bored with the low level of crime in Hometown, indicating that she would prefer to have some sort of action occur during the course of her duties. She eagerly looks forward to beating up any criminals or wrongdoers, is good at sports, and plays the piano.
Undyne sometimes plays piano at the local hospital. She plays well, but they ask her to leave if she starts singing.
After Kris returns from the Dark World, Undyne can be found standing in the street near the Hospital, where, instead of directing traffic, she has been standing in the street and yelling at everyone to get out of her way. If approached, she admits she has been feeling antsy lately because nothing ever happens in Hometown. She knows Kris as "Asgore's kid," but does not recognize Alphys's name.
If offered help from Kris, she suggests that they get someone to rob the bank "so I can suplex them," but since Hometown has no bank, she changes the request to getting someone to build a bank instead. If the Dark World is mentioned, Undyne laughs that having a Dark World at School isn't illegal and is therefore a matter for the school board. She also asks for any leads about a "purple girl" who is "wanted on several counts of Comic Mischief."
Undyne is first seen in a traffic jam at the crossing after the Library lifting one of the cars.
After coming back to Hometown, she can be found at the police station. Talking to her causes her to break her table and launch the cell key into the cell door, causing the prisoners that were there to flee, with Undyne chasing them, but not before she gives Kris a Box of Heart Candy.
During the final cutscene, Toriel is shown calling a police officer, probably either Undyne or Napstablook, about her car's tires being slashed.
- In a reference to Undyne's oft-repeated battle cry in Undertale, the caution tape blocking the road to the left of Hometown's Police Station reads "NGAHHHHH!!!" She also calls Kris "you punk," using the phrase in the same manner as her counterpart did.
- Undyne's line "Nothing to report, huh? At times like this... Punks like you should be home playing video games." is a reference to a line said by Captain Strong in EarthBound, which goes "At times like this, kids like you should be playing Nintendo games."