Commander Keen in Aliens Ate My Babysitter (stylized as Aliens Ate My Babysitter!) is a side-scrolling platform video game developed by id Software and published by FormGen in December 1991 for DOS. It is the seventh episode of the Commander Keen series, though it is numbered as the sixth, as Commander Keen in Keen Dreams is outside of the main continuity. The game follows the titular Commander Keen, an eight-year-old child genius, as he journeys through an alien world to rescue his kidnapped babysitter. The game feature Keen running, jumping, and shooting through various levels while opposed by aliens, robots, and other hazards.
After the success of the three-episode Commander Keen in Invasion of the Vorticons, the developers of the game, including programmers John Carmack and John Romero, designer Tom Hall, and artist Adrian Carmack, left their jobs at Softdisk to found id Software. After making a prototype game in Dreams to develop new ideas such as gameplay changes, graphical enhancements like parallax scrolling, and artistic improvements, the team worked on making a sequel trilogy of episodes from June to December 1991. During development the last episode was split off to be released as a stand-alone game due to a deal made by id's new president, Mark Rein, with the remaining two episodes produced as a pair titled Commander Keen in Goodbye, Galaxy instead. Aliens, despite being released as the sixth main episode in the series, was developed before the fifth. It did not sell as well as the first trilogy, which was attributed by id to poor marketing and its awkward status as a stand-alone retail game in a series known for groups of shareware episodes. Although another Keen game was planned, during development id Software began work on Wolfenstein 3D, and its success, along with the development of Doom, led id to not develop any further Keen games.
Gameplay
Commander Keen in Aliens Ate My Babysitter is a side-scrolling platform video game: the majority of the game features the player-controlled Commander Keen viewed from the side while moving on a two-dimensional plane. The player can move left and right and can jump, and can use a pogo stick to bounce continuously and jump higher than they can normally with the correct timing. The levels are composed of platforms on which Keen can stand, viewed from slightly above. Some platforms allow Keen to jump up through them from below, while others feature fireman's poles that Keen can climb up or down. Keen can also grab onto the edge of platforms and pull himself up. There are giant switches which must be jumped up into or dropped onto to flip which have effects on the gameworld, such as retracting and extending gates or initiate moving platforms. Once entered, the only way to exit a level is to reach the end, though the player can save their game at any point. Between levels, the player travels on a two-dimensional map, viewed from above; from the map the player can enter levels by approaching the entrance or save their progress in the game. Some levels are optional to enter and may be bypassed, while portions of the map are gated off until specific levels are completed.
The game contains a variety of enemies in the levels, which the player must stun or avoid; these are primarily different alien creatures. Levels can also include hazards, such as dart traps or fire; touching a hazard or most enemies causes Keen to lose a life, and the game is ended if all of Keen's lives are lost. Aliens has three difficulty settings, which change the number and types of enemies present. It features a stun gun that knocks out most enemies permanently using ammo found throughout the game. Different enemies take differing numbers of shots to knock out, or, in some cases, are immune. The player can also find food items throughout the levels which grant points, with an extra life awarded with enough points. There are also small fly-like creatures which award an extra life for every 100 collected, colored keycard gems which grant access to locked parts of levels, and items which instantly grant an extra life.
Plot
Despite being the sixth episode in the series, Aliens is not clearly stated to take place after the events of the pair of episodes in Galaxy. In the game's introduction, eight-year-old child genius Billy Blaze is working on his wrist computer in his backyard clubhouse when his babysitter, Molly McMire, calls him in for dinner. Upon hearing a loud noise he rushes out, only to discover her missing and a note burnt into the grass stating that the Bloogs of Fribbulus Xax have taken Molly and plan to eat her; donning his helmet as Commander Keen, Billy rushes off to save her before his parents get home. During the game, Keen journeys through the various outposts, factories, and installations of the alien Bloogs on the planet of Fribbulus Xax as well as a space station above it.
After Keen finds Molly tied up at the back of the Bloog Control Center on the space station, she explains to him that she was kidnapped on the orders of her younger brother, who Keen knows to be his nemesis Mortimer McMire. Mortimer convinced the Bloogs to kidnap her by offering them the Stupendous Sandwich of Chungella IV. Keen is surprised, as he thought Mortimer was dead (he was apparently killed at the end of the Vorticon trilogy), and is dismayed to find out that Mortimer plans to blow up the entire universe. This conclusion is also revealed in an encoded note at the end of the Galaxy. The game ends by asking the player to play the next installment, where Keen would again fight Mortimer.
