The Glad Dummy is the optimistic version of the Mad Dummy, his Undertale counterpart. He is usually helping Frisk with assistance throughout his moments in the game.
The Glad Dummy helps Frisk for a portion of the game, but departs after a certain point when he goes to try and make his cousins Napstablook and Mettaton make up. He also appears in the final battle in the pacifist route for support along with the other characters. During a Genocide Route, Glad Dummy will fight the player and become Mad Dummy.
The Glad Dummy, similar to Flowey, spares you to begin with.
Battle (Mad Form)
in the Genocide Route, Glad Dummy turns into Mad Dummy, and tries to stop frisk by using dummy attacks and rocket bombs. Unlike the original fight, He also throws lots of knives in the last phase, which can one shot the player. He cannot be killed like his underfell form, but, at the end of the fight. Napstablook kills Mad Dummy with his tears and the battle ends.