Why is Tybalt called Prince of Cats?

Mercutio refers to Tybalt as the "Good King of Cats" or the "Prince of Cats" because his demeanor and actions are much like a cats': lithe, agile, predatory and territorial. Tybalt is hot-tempered and quarrelsome, as we see by how quick he is to engage in battle.

But the "Prince of Cats" title also stems from an earlier time, an earlier tale. There is a fable called "Reynard the Fox", in which one of the characters is a cat named Tibert/Tibalt/Tybalt that is called the "Prince of Cats". This character was also quite quarrelsome, as the Tybalt of Romeo and Juliet was.

Because he has nine lives.

because he loves LASAGNA!

The word "cats" is similar to the Italian word "cazzo" with means pelvis or penis since Romeo and Juliet is set in Verona, Italy Mercutio could be suggesting that Tybalt is king of men in terms of sexual organs.

Don't quite understand why Mercutio would suggest that but that is what my English teacher said.

It's because of his stealthiness in the art of sword fighting

pussy king