Okay, never mind. Bad suggestion. Frisk has studiously avoided bringing up anything of the sort to Asriel, partially out of fear and partially because it's doubtful he'd want to talk about it anyway. If they're going to talk about it, he should be the one to bring it up, shouldn't he? No point in prying.

So Chara changes the subject. Frisk lets them. Tries to laugh, even if it sounds forced.

"I saw that video he put up." A bit overkill, they think, but...he's having fun, and it was for Asgore's sake, if what he said held any water. "Little less scary once you know who he is. Pity he can't do all those flashy rainbows!"

Or can he? They...didn't ask. But anyway, it's a costume. Meaning that's not who he is at his core, which is the most important thing.