Chica was the fifth animatronic to appear on Eth's channel and hasn't been known to play many games. Her most memorable moment is when she played Can Your Pet (and we all know how that went). It wasn't until her third appearance that her companion on a plate, The Cupcake, appeared in a video with her. This same appearance was also the first times Eth made multiple characters play a game, these characters being Bonnie, Chica, and Cupcake.
Ever since then, The Cupcake has always been with Chica every time she shows up. There was even an animated short about them. The only time that the Cupcake hasn't been with Chica after this change was when she played night three of POPGOES, which was later revealed to be a theory being told by the Puppet.
Personality wise, Chica is a very kind-hearted animatronic, with two main things in mind: pizza and Cupcake. She has never had any moment of anger or sadness, only the realization that people eat chickens, which caused her to throw up. She also loves cooking. This might be the reason why she barely appears in videos. She is presumed to be in a romantic relationship with Bonnie, but this is not confirmed.
She was a victim of the Fazbear Massacre (along with her cupcake) and became a phantom. Thus, she fell under Springtrap's control and worked to kill the remaining Fazbear residents. Her cupcake however helped the remaining residents fix what Springtrap broke.