What's a yak's favorite drink? CognYAK
What do you call a yak who wants to take over the world? A megalomaniYAK
What do you call a yak with a blood disorder? A hemophiliYAK
Who's the most dangerous yak of all? YAK the Ripper
Why did the yak go to the emergency room? Because he was having cardiYAK arrest.
And while he was there, he decided to have his catarYAKs removed.