UFOs, or Unidentified Flying Objects, make appearances in the SNES game EarthBound where they were implied to be employed by Giygas in his takeover of Eagleland. They also appeared as enemies, however, in that state they were small, cute-looking, apparently sentient beings called Li'l UFOs.
As a platform
On the Fourside stage, the same UFOs sometimes descend into the stage, serving as hovering platforms. They are also very slippery, so it's easy to get KOed. They have green lights on the bottom, and the noise they make when entering the stage is similar to the sound effect used in the title screen of EarthBound when the attack scene faded in.
As a trophy
At the beginning of EarthBound, this flying saucer appears along with the ominous message, The War Against Giygas! Adding to the mystery are three more UFOs while fly amok in the skies over Onett; how all of these alien craft are connected is anyone's guess. In Super Smash Bros. Melee, this slippery UFO appears on the Fourside level.
Game: EarthBound (06/95)