Grumpy Cat

Grumpy Cat, real name Tartar Sauce, is a real-world Internet meme. She is a cat known for her facial expression, which appears grumpy. She has a minor role in Yu-Gi-Oh! The Extended Edition.

Mahad's Backstory
Grumpy Cat makes her first, and only, appearance as a part of Dark Magician's backstory. She appears to him in spirit following his death at the hands of Thief King Bakura.

Dressed as a Sphinx, Grumpy Cat offered to save Mahad's life, in exchange for granting him 'dank memejix'. Mahad quickly agreed to the deal, and Grumpy Cat merged into his body and granted him the memejix. She is never seen or referred to again after this.

Trivia

 * Despite making no subsequent appearances, Grumpy Cat has a huge impact on Yu-Gi-Oh! The Extended Edition, as without her, Mahad would've never become Dark Magician.
 * Grumpy Cat was chosen to give Mahad his powers by Joanne, who stated, "I wanted Dank to have gotten his powers from a real meme, and cats were everywhere in Egypt."
 * Grumpy Cat could potentially be a Goddess of Memes in Egypt.