Mad Dummy

Mad Dummy is a ghost monster living inside a dummy located in the Garbage Dump. They also serve as a mini-boss in Waterfall.

Appearance
Mad Dummy takes the appearance of a dummy with a set of upper teeth on the torso, a set of eyes on the head, and nostrils on the nose. However, as Glad Dummy, they will instead have two happily closed eyes and a smile.

Neutral Route
When Mad Dummy is encountered at the Garbage Dump in Waterfall, they reveal that the dummy in the Ruins was possessed by their cousin.

Regardless of how the protagonist interacted with the first dummy, Mad Dummy will be enraged by it. They attack the protagonist with the intentions of stealing the protagonist's soul. The fight is later stopped by Napstablook. After the fight, they will be found outside of Undyne's House taking a job as a punching bag.

True Pacifist Route
In the True Pacifist Route epilogue, the dummy will remark about the barrier being destroyed and express their apology to the protagonist for "being a dummy."

Genocide Route
When encountering Mad Dummy in the Genocide Route, the amount of hatred directed towards the protagonist's actions allows them to "fuse with their body," fulfilling their lifelong wish. As a reward, they are willing to spare the protagonist as soon as combat begins. Unfortunately for the newly-renamed Glad Dummy, they are now vulnerable to physical attacks.

If the protagonist decides to abandon the route for Glad Dummy, they can be found outside Undyne's House and will continue to thank the protagonist for their corporeal form.

In Battle

 * See Mad Dummy/In Battle

Trivia

 * The music played before the Mad Dummy fight is similar to the track "Apparent Crisis" from JoJo's Bizzare Adventure: Stardust Crusaders' soundtrack "Destination."
 * Mad Dummy makes several possible references to JoJo's Bizarre Adventure: Stardust Crusaders.
 * They yell out "Foolish. Foolish! FOOLISH!", "Futile. Futile! FUTILE!", and other words repeatedly similar to how DIO would repeatedly yell out . They also pull out and throw a knife which alludes to how DIO pulls out and throws a multitude of knives.
 * In addition to this, Mad Dummy is later seen outside of Undyne's house, taking a job as a punching bag. This arrangement may be another reference to DIO and his Stand, The World as both are adorned with green hearts while Undyne can turn the protagonist's soul green.
 * It is stated that one of Napstablook's cousins also went to possess a training dummy, but it is not confirmed if either Mad Dummy or their cousin is related to Napstablook's cousin at all. In fact, after interrupting the battle, Napstablook refers to Mad Dummy as the protagonist's friend, suggesting that the two might not be related.
 * Like Dummy in the Ruins, repeatedly missing attacks/checking Glad Dummy will make them "tired of the protagonist's aimless shenanigans" and leave.
 * At the end of the fight, Mad Dummy tries to defeat the protagonist by holding their turn forever. This tactic is also used by Sans at the end of a Genocide Route, but both times the technique fails.
 * The introduction scene for Mad Dummy may be a reference to the "Gutsman's Ass" scene from the Mega Man.
 * On the Genocide Route, regardless of how the protagonist acts towards the Dummy in the Ruins, it does not affect Mad Dummy's dialogue. They will continue to tell the protagonist that they have destroyed their cousin's home.