Fester's Quest is a video game for the Nintendo Entertainment System based on the 1960s television series The Addams Family. Assuming the role of Uncle Fester, the player embarks on a quest to save the Addams' town from an alien invasion. Along the way, Fester encounters Addams Family characters such as Thing, Wednesday Addams, and Pugsley Addams, all of whom help him by giving him with different weapons and items. The game uses Blaster Master's overhead shooter engine.
The three overhead-view areas are:
- Outside street: Fester has to traverse around town to get from place to place. Hot dog stands, houses, and buildings are located above ground.
- Underground sewers: Some street areas cannot be accessed directly, but can only be reached by entering the sewer tunnels that run underneath the entire city.
- UFO Platform: Five Alien Bosses will challenge Fester during the game. After they have all been defeated, the way to the UFO Platform will be revealed. Here, Fester must find and destroy the ship's control center in order to complete the game.
Fester may enter certain buildings, which transform the game from its standard overhead view into a 3D mode of play akin to a dungeon crawl. In most buildings, Fester encounters one of five enormous Alien Boss characters, which upon defeat will supply him with a puzzle piece (a picture of the alien's UFO) and refill all of his items. After defeating a boss, Fester will leave the building and be unable to backtrack through it to previously visited areas.
During Fester's quest to stop the aliens, he can collect several different items, most of them provided by a member of the Addams Family.
- Gun: Fester has this item when he begins the game. Defeated enemies sometimes drop blue or red "GUN" icons, which power the weapon up or down, respectively.
- Whip: Fester's second weapon can be obtained from Morticia Addams. It can be powered up/down by collecting blue/red "WHIP" icons, and it can strike enemies through barriers such as walls and bushes.
- T.N.T.: Fester can obtain T.N.T. from Pugsley Addams. It detonates a short time after being dropped, and can be useful in defeating certain enemies.
- Vice Grip: Wednesday Addams will give these to Fester; he can use them to return to normal movement speed after being paralyzed by certain enemies.
- Potion: The first of three items provided by Thing, the potion completely refill's Fester's health meter.
- Invisibility Potion: Thing's second item. Makes Fester invincible for a short time.
- Missile: Thing's third item. Any on-screen enemy can be targeted with this weapon.
- Noose: Given to Fester by Grandmama. When used, Lurch will appear (complete with shaking gong noise and "You rang?"), and immediately destroy all on-screen enemies.
- Money: Commonly dropped by smaller enemies. Fester can use the money to buy hot dogs at stands all over the city to restore lost health.
- Light Bulb: Fester has to use these to find his way in the dark sewers.
- Key: Used to gain access to houses and buildings.
- Life Bar: Fester begins the game with two boxes in his health meter, but he can obtain up to two more by visiting certain buildings.
- Globule: A small pod that sits on the ground.
- Hopper: These frog-like enemies are seen all over the place and come in four colors: Blue, which hop straight toward Fester; Red, which hop about randomly, Green, which both pursue and lash out with their long tongues; and Pink, which can spit paralyzing fireballs. Green and Pink Hoppers can take twice as much damage as Red and Blue Hoppers.
- Skeeter: Immobile floating heads that release paralyzing bugs and worms when shot.
- Rat: A common sewer rat. It's only dangerous to Fester if it bites his feet.
- Slime Replicator: Multiplies into several copies of itself when shot.
- Slime Snail: This enemy creeps slowly towards Fester. Once defeated, it will turn into a Slime Replicator.
- Bugg: Hopping enemies in the city streets that leap away from Fester's shots.
- Arachnid: A giant spider that appears when Fester has stayed in one area for too long.
- Big Mouth: A pink mouth-like slug that can burrow under walls.
- Eye Pod: A cyclops beast that is orbited by three deadly blasters.
- Mr. I: These are eyeballs that jump up and down chasing Fester.
- Grabber: A giant green monster with long arms. These will run toward Fester if they detect him.
- Alien Pod: A pod-like creature which will randomly walk around then "open up" and shoot poison balls. Unlike Pink Hopper's paralyzing fireballs, these poison balls take off health.
- One of the more common enemies, namely the frog-like Hoppers, are actually miniaturized versions of the frog boss from Blaster Master, another Sunsoft game.
- Most of the sound effects are from Blaster Master.
- A secret level accessible with the Game Genie device allows Fester to watch schoolchildren play in a park. The goal of this level is not clear, but it's possible it was an area cut from the final game but not removed from the game's data.