Human Pandora

A person who listens to a certain word and starts singing a known song relating to the word. Almost like a radio on demand.

If you are on the phone or sitting face to face with such a person and you ask "Did you see the fireworks display?", the person will take the cue from the word and start singing "Baby, You are fireworks!" by Katy Perry.

Dude, You gotta talk to her, She's a Human Pandora.