Character nicknaming is a trend of certain users who are give characters (whenever an original character, a videogame character or an anime character) a simliar name of another character, a person, a company or brand, and/or miscellaneous things.
The trend was started by Jashin Empress on February 29, 2016 from the Midori Hario article on the GoAnimate 2 Wiki (called nowadays as FanonLand Wiki) -- where Midori got nicknamed as Midori Mario, due to "Hario" and "Mario" sounding similar. Some weeks later, some users have picked up on it and started nickname other characters (mostly OCs), soon it expanded to include video game characters, anime characters, and (in some cases) the real life people (particularly whose ethnicity is (half-)Japanese).
There are two common methods of nicknaming certain characters -- it's either the similar name or an approximately exact first or last name of another character.
This nicknaming method is the most commonly used out of all other types. The characters' name gives the similar namings that might sounds similar or rhymed. In some cases, the partial letters of their names would give them nicknames by users.
- Kuniyo Ebisawa → Kuniyo Ebisuzawa (Kurumi Ebisuzawa, School Live!)
- Ayase Sasozaki → Ayase Sasori (Sasori, Naruto)
- Seijou Mizushima → Senju Mizukage (Senju and Mizukage clans, Naruto)
- Junko Mukawa → Junko Fukawa (Toko Fukawa, Danganronpa)
- Hanamaru Kunikida → Hanamura Kunimitsu (Teruteru Hanamura, Danganronpa 2 / Kunimitsu, Tekken)
Same family name/Same first name
In this nicknaming type, characters that share the same given or family name are dubbed with the exact name of another character.
- Eri Tategami → Eri Kitamura (Japanese singer and voice actress)
- Alisa Ayase → Alisa Bosconovich (Tekken)
- Yoko Ran → Yoko Littner (Tengen Toppa Gurren Lagann) or Ran Yakumo (Touhou Project)
- Akane Samezawa → Akane Owari (Danganronpa)
- Nico Yuri → Nico Yazawa (Love Live!)
- Kirino Kousaka → Honoka Kousaka
Other nickname types
The fad can also expand into country naming if the character has a country's name on his/her name (Chinatsu Yoshikawa for example, due to her name having "China" on it, is given nicknames that replace "China" with name of another country, such as Brazil).
It also can expand into mentioning other users if a character's name has the pronoun "You" on it. (You Watanabe for example, who often is dubbed as "[Your username here] Watanabe".)