Cassette vs DVD

We we're reading Judi and Ron Barrett's "Cloudy With a Chance of Meatballs" when one of the students said the she had the movie with same name. There is a movie made based on the book (film adaption) in 2009. I asked her if she could bring the movie, and she said she would bring the cassette.

The cassette? To make sure what kind of cassette she would bring so we could prepare the right player. So I asked her if the cassette is a large kind (means it's a VHS cassette) or a smaller one (means we need a Beta player). Then she said,

"Huh? It's small and circular and thin like a plate."

Okay, so NOW they call a disc, cassette.