MTJJ 

MTJJ is an abbreviation of 摩托姐姐 (mó tuō jiě jiě) which is one of the ways to call fan/fandom of Chinese Actor/Singer/ Motorcycle racer Wang Yibo. The original name was YAMAHA, named by Wang Yibo in a variety show in 2017. He used this name because he loves racing motorcycles and his motorbike's brand is Yamaha. But because of the copyright problem, his fandom changed the fandom's name to 小摩托 ( xiǎo mó tuō) means small motorcycle.
In the beginning, most of Wang Yibo's fans are women and older than him, so his fans use MTJJ to call themself. MT(摩托-mó tuō) means motorcycle and JJ (姐姐-jiě jiě) means elder sister. But nowadays, Wang Yibo's fandom is huge with all age ranges, so his fans also use MTGG (摩托哥哥 -mó tuō gē ge means elder brother motorcycles); MTMM (摩托妹妹-mó tuō mèi mèi means younger sister motorcycles); MTDD (摩托弟弟-mó tuō dì di means younger brother motorcycles) to call themself. Wang Yibo's fans also call themself are cats because MT (mó tuō ) sounds similar to a cat in Chinese ( 猫头-māo tóu)
Summary, 小摩托 ( xiǎo mó tuō)/MTJJ/ MTGG/MTMM/MTDD/ Cat are use to call fan/fandom of Chinese Actor/Singer/ Motorcycle racer Wang Yibo. They are a huge community that only loves and supports Wang Yibo.

Ask: Are you a fan of Wang Yibo, just only him and not shipping him with anyone?
Answer: Yes, of course. I'm a MTJJ for sure.

MTJJ by tinygreenleaf January 26, 2022

MTJJ 

Person who loves and supports Wang Yibo unconditionally
MTJJ stands for 摩托姐姐 (mo tuo jie jie) - motorcycle sister
Nickname: Cat Head because MT (motuo) sounds like maotou 猫头

Color: Green

New fans: I am a fan of Wang Yibo? What can I be called as?
Answer: MTJJ!!

MTJJ by Cncats January 26, 2022

MTJJ 

MTJJ stands for Motuo Jiejie, Chinese 摩托摩托车, what means motocycle sister. It is a name of actor Wang Yibo's fandom simply because he likes motorcycle so much (he is also a motocycle racer).

MTJJs love Wang Yibo so much!

MTJJ by Jjie January 26, 2022