Bunny the Grouch

 Bunny  is Oscar the Grouch 's sister & the sister of  Ernest  &  Otto the Grouch. She appears in episode 4237 as a surprise guest for Grouch Mother's Day. Oscar 's mother  gave Bunny her name just to annoy her.

"Was your mother also a Grouch? Oh yes, I come from a long line of Grouches. I have a sister, her name is Bunny. Mom named her that just to tick her off. She’d rather have had a name like Geezelah or Grumpy, because she is, trust me, a grump. Do you see her often? Hopefully not, although it is kind of fun when she comes because we argue the whole time. Grouches like a good argument. I’m only worried about this because I haven’t been disagreeable enough. I guess I got out of the right side of the bed. You’re too pleasant. ... & I love being miserable. That makes me happy. But I don’t like being happy, so that makes me miserable. I’m a mess. I’m a complex Grouch."