Scooby-Doo and Scrappy-Doo

Crazy Carnival Caper (5x16)

: 15, 1983

The kids go back to their high school for the Central High Carnival, and run into their old science teacher Mr.McDabble, who has created a ruby lazer that can cut through the hardest metal. But before too long, the ruby ends up missing, and the kids have to find out what happened.