Cat Boy

In anime, a cat boy is a character that has cat-like features, such as feline body parts—"cat ears," nekomimi 猫耳, "cat eyes," nekome 猫目, "cat mouth," nekoguchi 猫口, and a "cat tail," neko-shippo 猫しっぽ—and ending their sentences in nyaa にゃー, "meow."

Character: Ferris フェリス
Anime: Re:Zero kara Hajimeru Isekai Seikatsu Ｒｅ：ゼロから始める異世界生活 (Episode 12)

• In Japanese
• Types
  
  • Natural
    
    • Anthropomorphized
  • Cosplay
• Tropes

In Japanese

The most common way to say "cat boy" in Japanese would be nekomimi-danshi 猫耳男子, "cat-ears boy." In general, if a character has cat ears they probably have a cat tail, too, but that's not necessarily true.

You can combine either neko 猫, "cat," or nekomimi 猫耳, "cat-ears," with a noun that means "boy" to create a word that means "cat boy" or "cat-ears boy." Unfortunately, there are various words that mean "boy" in Japanese. For reference:

• nekomimi-shounen
  猫耳少年
  Cat-ears boy.
  • shounen
    少年
    Underage person. (legal term.)
    Boy. (normal usage.)
• nekomimi-otokonoko
  猫耳男の子
  Cat-ears boy.
  • otokonoko
    男の子
    Male child.
    Boy.
• nekomimi-otokonoko
  猫耳男の娘
  Cat-ears trap.
  • otokonoko
    男の娘
    Male girl. A girl that's actually a boy. A boy that looks like a girl. A trap.
• nekomimi-seinen
  猫耳青年
  Cat-ears boy.
  • seinen
    青年
    A young adult man.
• nekomimi-shota
  猫耳ショタ
  Cat-ears boy.
  • shota
    ショタ
    Boy anime character. (male counterpart of loli.)

Similarly: neko-danshi 猫男子, neko-otokonoko 猫男の子, neko-shounen 猫少年, neko-seinen 猫青年, neko-shota 猫ショタ, and so on.

The same thing also works if you switch "boy" for "man."

• neko-otoko
  猫男
  Cat man.
• nekomimi-otoko
  猫耳男
  Cat-ears man.

Types

There are various types of cat boys that can be found in anime.

Natural

Some characters are born with as cat boys, with cat ears and tail attached to their bodies.

Left: Aoyagi Ritsuka 青柳立夏
Right: Soubi Agatsuma 我妻草灯
Anime: Loveless (Episode 1)

• In Loveless, only virgin characters have cat ears. That is, everyone is born with cat ears, and you lose your cat ears as you lose your virginity.

Anthropomorphized

Some cat boy characters are supposed to be anthropormizations of actual cats. See also: gijinka 擬人化.

Left: Okamoto Tama 岡本タマ
Right: (same character)
Anime: Uchi Tama?! Uchi no Tama Shirimasen ka? うちタマ？！～うちのタマ知りませんか？～ (Episode 1, OP)

• In the Uchi Tama?! anime, all animal characters are drawn like animals when interacting with humans, and drawn like people when interacting with each other.

Cosplay

Some characters wear cat ears to cosplay as cat boys.

Character: Shiina Aki 椎名亜樹
Anime: Sunohara-sou no Kanrinin-san すのはら荘の管理人さん (Episode 3)

• josou
  女装
  "Female-clothes." Also a term for crossdressing.

Tropes

See: Cat Girl for common things and terms related to cat boys.

It's worth noting that neko ネコ is a LGBT slang for "bottom" in a homosexual relationship.