Costume Quest is a party-based role-playing video game developed by Double Fine Productions and published by THQ on October 20, 2010.

In the game, the player controls a child who is trick-or-treating with their twin on Halloween night when they encounter a monster that kidnaps their sibling.

The player must travel around the local neighborhood collecting items for their costume, candy, and fellow children as companions in order to face the leader of the monsters and rescue their sibling.

A DLC expansion titled "Grubbins on Ice", was released on December 21, 2010, taking place after the events of the original game and set in the monster world of Repugia.

Battles are turn-based, allowing the player to select attacks, blocks, or a special move that requires hitting a quick time event at the right moment to achieve maximum damage to their foes.

[6] The player character trick-or-treats at houses, tracking the monsters and their sibling from the neighborhood, then to a mall, and then to a country town.

Similar to the original game, the player must trick-or-treat at various houses to eventually reach Cadaverous Big Bones, defeat him once more, and rescue Lucy.

At the end of "Grubbins on Ice", the main characters escape from Repugia into a nexus of portals, which leads directly into the plot of Costume Quest 2.

Costume Quest is a result of a series of "Amnesia Fortnights" that Double Fine had used during the period of Brütal Legend's development when they were unsure of their publisher.

Instead, Tim Schafer turned back to the Amnesia Fortnight products and sought to develop those as smaller games among several publishers.

[6] Costume Quest's development was led by Tasha Harris, Double Fine's lead animator and a former Pixar artist, with Tim Schafer providing support where needed, particularly in writing.

The time frame and team size were based on Schafer's previous experience in developing The Secret of Monkey Island.

[9] The shortened schedule forced them to limit the scope of the game and prevented "feature creep", the addition of interesting but unnecessary gameplay elements.

[14] The original Costume Quest prototype was released for Microsoft Windows as part of the Amnesia Fortnight 2012 bundle on November 19, 2012.

[15] An additional downloadable chapter, "Grubbins on Ice", was made available on December 21, 2010, alongside a free patch to correct some of the game's performance and gameplay problems.

Wren and Reynold return in the sequel, which introduces more costumes and features a "deeper and juicier" battle system according to Schafer.

[23] The game's plot involves Wren and Reynold traveling into both the past and the future in order to undo the actions of the evil time-traveling dentist Dr. Orel White, DDS.

Gorman had previously drawn a Costume Quest comic for his Magical Game Time webcomic series, which got the attention of Double Fine and led to this collaboration.

Having worked on the original short, Zac Gorman was initially approached as showrunner, but turned it down, though his style became crucial to the show's look, and he contributed as a writer on 2 episodes.