Looks like BS to me. I could be wrong though. It’s definitely not a recognized error card for sure.
bulbapedia.bulbagarden.net/wiki/Error_cards#Base_Set
Here is a video of someone showing off one of these Clefairy Heart cards:
There was discussion here before about a similar ‘misprint’ and mentions that this card was prone to ink bubbles.
www.elitefourum.com/t/the-name-for-this-kind-of-misprint-pokemon-card/12603/1