Games like Alien Function

If you finished Alien Function, the closest matches are Stormland, LEGO Island 2: The Brickster's Revenge, Pilot Brothers 3: Back Side of the Earth, Destroy the Porn and Chikyuu Bouei Shoujo Iko-chan: UFO Daisakusen. All 7 share its adventure genre and are ranked by how closely their themes and modes overlap.