Hooktail is a dragon in Paper Mario: The Thousand-Year Door that once terrorized Petalburg. She ate all of its residents who came to her castle to slay her, like Kolorado's Father, Old Man Skoo, and Koops' dad. Mario and Goombella first encounter the dragon in Petal Meadows, where you see her shadow pass over the area. When Mario, Goombella and Koops came to her castle to obtain the first Crystal Star, the Diamond Star, they were given a clue on how to defeat Hooktail once they found the dead body of Kolorado's father-- Hooktail cannot stand chirping sounds, especially ones that start with cr- and end with -icket. The reason for this weakness is because she got food poisoning from eating a Cricket. Some believe that it is a reference to the Toad of the Four Heroes, who is described as having a "strange voice". He defeated Hooktail long ago; his voice may have sounded like a cricket.

During the fight, it seems Hooktail is defeated, but before Mario and his team can finish her off, she swallowed some of the audience members to replenish 10 of her HP. Once Mario defeats her completely, Koops' dad will burst out of her mouth, since he's lived in her stomach.

She has two older brothers named Bonetail and Gloomtail. It was not revealed that Hooktail was female until the fight with Gloomtail. Koops's dad even said that "he" gobbled him up, which is part of the reason it is implied that Hooktail was male until fighting Gloomtail. Gloomtail attempted to defeat Mario and his friends for slaying his sister. There is some of the game's recurrent humour in this scene, as Gloomtail mentions Hooktail not writing to him.  Hooktail resides in Hooktail Castle, while Gloomtail was in a chamber in the Palace of Shadow, and her (presumably oldest) strongest brother Bonetail was on the bottom floor of the Pit of 100 Trials.

According to Grifty in Rogueport, the three siblings were once the pets of the Shadow Queen.

Later on in the game, when Mario and company revisit Hooktail's lair, they find no trace of Hooktail. Goombella wonders briefly where Hooktail disappeared to, but ends up deciding Hooktail's absence is a good thing.

In battle, Hooktail has two attacks. Her first attack is to stomp on Mario or his partner. She can also breathe flames on them.