In Once upon a time, they had the "heroine" (though by this point in the show the writing had gone downhill) stab her evil lover through the chest with a sword in order to save the town. It was a blatant Buffy rip off.
Just because Disney hasn't bought rights to the show yet doesn't mean they won't use (or mock) it...I think about everyone can see this is taken from Buffy (changing the vampires into zombies, and reversing the genders of Buffy and Angel):
I think my fave refs are the ones in Gilmore Girls and Bones because they're so specific. Like, most of the references are just saying the words "Buffy the Vampire Slayer", so you don't have to have watched the show to get it. But mentioning the Hyperion or Spike & Drusilla? You need to have seen the shows to get those references, so they're more nods to the fandom whereas the others are just general pop culture references.