Felidae

Cat (猫) is a small, usually furry, domesticated, carnivorous mammal.

Mega Man Zero 3
Several cats appear in the Resistance Base with the use of the Mod Cards #17 Hittite Hottide and #46 Panter Flauclaws.

Mega Man ZX
Cats with the same appearance as the ones from Mega Man Zero 3 appear in Area C as part of the background.

Mega Man Legends
Kattelox Island has several black cats. After defeating the Marlwolf, Mega Man Volnutt can go to the Main Gate's entrance and take one of the three cats roaming in the area to the Flutter. The amount of cats inside the Flutter increase as time passes, reaching up to 8 cats of varying size in the Living Room and 3 in Mega Man's Room. Mega Man is able to understand what some of them say. Also, later in the game one cat will appear in the Yass Plains and two in the Cardon Forest. Mega Man is able to kick cats in the Japanese version of the game, but his armor will become darker if he kicks them repeatedly.

The Misadventures of Tron Bonne
Cats appear Ryship Island during Tron Bonne's attack to Gold City. If the Beacon Bomb is used in a cat, the Servbots will try to get it, but it will growl and make them run away from it.

Other media
In the MegaMan NT Warrior anime series, Ms. Yuri adopted a cat she found in the street.

Trivia

 * In Mega Man Legends 2, Mega Man mentions that Kattelox Island had several cats in Kimotoma City.