I'm sorry, what do you mean by a hoover? Because the only thing that I though when I saw the word hoover was that your mother or someone was trying to vacuum up your Tamagotchi... ^__^
Ok, what generation of Tama do you have? is it a Music Star or something older? Also, is there an animation on the screen that your talking about? like the UFO floating by?
By the way, if there is a UFO floating on your screen... there's nothing you can do, your Tamagotchi has kinda died... or gone back to Tama Planet, however you view it