Lying to a fish is such an unthinkable act, most planets don't even have a law against it.

Blufferfish

{3}{U}: An opponent tells you a statement about themselves and secretly notes whether it's true or false. You guess which it is. If you guessed correctly, this creature gets +2/+0 and can't be blocked this turn.

Unfinity

The opponent is the authority on whether the statement they make is true or false. That said, lying isn’t allowed, and they should be sporting about it.

The statement the opponent makes doesn’t need to be very personal, but it does need to be about themself. Something like “I had eggs for breakfast” is fine.