Fake Loading Screen
An endless "Installing updates..." screen to leave on a shared display — it never actually finishes, and never actually does anything.
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About this tool
This leaves an obviously-a-joke "endless loading" screen up on a shared device for a laugh — it never performs any real update or install, and no real progress is ever made (that's the joke). Use it on a device you're allowed to mess with, with people who'll find it funny.