Baby Bus
From The Project 2

Origin
This joke originates from the Karate Camp, where a kid was once playing a game on his tablet, and another kid pointed at him and said "HE PLAYIN' BABY BUS", to which the first kid got extremely upset, and after 2 days of constantly mentioning this, he cried, and we stopped.
Usage
Mentioning Baby Bus as if it is a real game, and other stuff, this one is kinda hard to define.
Possible link?
There is a real company called "Baby Bus" that does make games, so it's very possible he was playing a game by Baby Bus.