I've been staring at that Undertale post forever I'm sorry but how in the world is that a pun I'm so dumb
I take it you’re unfamiliar with the final fight (spoilers by the way).
In the last fight of the True Pacifist run, you go up against Asriel Dreemur, and during said fight, if your hit points go down to 0, this happens:
(skip to 7:03 if the link isn’t starting at that point)
Up until this point, if your HP reaches 0, you get the game over screen. Here however, the heart fuses back together and the fight keeps going (the “but it refused” message only appears the first time this happens, though). So, does it make sense now?
The heart refuses to stay broken because of the power of DETERMINATION, but at the same time, it’s a pun because the heart is literally re-fusing together, as in both parts are combining back into one whole heart again.
