The three seashells from Demolition Man confused audiences into wondering how this futuristic toilet paper (three scallop shells lined up on a bathroom counter) was supposed to work. Many fan theories exist, including one by Sandra Bullock, who was still getting questions about it twenty years later.
In Ghostbusters (1984), Venkman enters Dana's flat operating a strange device with a long tube and a rubber bulb that appears to pump air through the tube. When she asks what it does, he replies vaguely "It's... technical. One of our little toys." The commentary reveals that Bill Murray was given a selection of tools to choose from, and thought that one was the funniest. It's actually a device for detecting noxious gasses in the air, used by sewer workers.