Mr. Fantasy Asked If He's Actually 'Riverdale' Star KJ Apa, Dodges Question

Still trying to figure out if Mr. Fantasy is actually KJ Apa? Yeah ... good luck with that -- 'cause when we asked him straight up, the guy got real weird.

TMZ caught up with the eccentric Brit in Hollywood Tuesday ... watch the video, as things quickly took a bizarre turn when we pressed him on the rumor he's the "Riverdale" star. Let's just let the video do the talking ...

We tried our best -- even asking how often people mistake him for KJ -- but he kept insisting he had no idea what we were talking about.

Still, it does raise a question ... if he’s not the New Zealand-born actor, why not just say it?🤔

For those out of the loop -- Mr. Fantasy is a mysterious new musician who’s popped onto the scene while keeping his real identity under wraps. Fans are convinced he's KJ Apa's alter ego ... and if that’s the case, he’s clearly committed to the bit!