-oneechan

oneechan is a Japanese honorific used to refer to ones older sister. Apple Bloom of the Apple Clan referred to Applejack as her oneechan.

Meme
An older My Little Pony: Friendship is Magic meme circulated in 2012 revolving around saying "oneechan" and Dan Mandel getting violently angry, with audio from The Whitest Kids U'Knows Abe Lincoln sketch. The video can be watched below but contains adult language.