Your characters must include a disguised scientist, a paranoid detective, and a reckless taco salesman.

One must be 70 or older. Another must be 13 or younger. These characters must work together to meet some end.

Samples:

The Three? by Lexi Anders

The Taco is the Job by Natasha Blade

Termites, Teacher and Taco Sauce by Hannah Christensen

Crazy Cases by ED Nobody