If you know enough about the topic, whatever you say doesn't have to be true. Look up a few rock climbing locations around you and claim to be a rock climber. Now you need to know some basics in case someone asks a follow up, like where have you climbed?

No one will double check your "fun fact" as long as its not too crazy. No saying you've gone to the moon or played guitar in msg. Your favorite food was Gordon Ramsey beef wellington? Doesn't matter if you ever actually ate it. Just know that it's not a stew.

How about telling an interesting fact about yourself?