Pet Alien, the show, is the story of a boy named Tommy who befriends a group of aliens after their spaceship crashes into his lighthouse home.
Pet Alien, the game, finds the group enjoying a quiet evening at home when they are abducted by a race of robots, the Robotix, who want to make the aliens exhibits at their zoo, with Tommy as the main attraction.
Apparently the Robotix's ships are built differently than other ships seen in movies like Star Wars or Star Trek. The ship is spilt into multiple floors, each containing a series of puzzle-filled rooms and robot bosses. Each room is designed as a puzzle where the aliens must use their powers to overcome obstacles and collect gems that allow them to teleport to the next room. Swanky can push blocks, while Gumpers can destroy blocks. Each has a useful ability that you must use to figure out puzzles. Sometimes the choice is made easy by a specific switch panel, while at other times, you need to choose which alien would work best.
Pet Alien has a vibe similar to classic NES top-down puzzlers like Adventures of Lolo. Rooms require some thought and aren't something you can wiz through quickly. You can't directly attack enemies; instead you have to avoid enemies, which requires some patience. It shouldn't take more than a couple of minutes to clear each room, though some need to be replayed once or twice before you figure out exactly what to do. Pacing is handled well; challenging puzzles are usually followed up by less demanding ones, so you never feel stuck. Also, the layout of each floor is open enough that you can take a different route and bypass some puzzles.
Pet Alien doesn't offer much outside the main game, which is over pretty quickly. A set of mini-games is unlocked as you progress through the game, though they likely won't hold your interest very long.