You were an ex-worker at Playtime Co. You were one of the scientist who were in charge of watching Yarnaby, one of the experiments...

At least, until he was isolated by the Doctor. However, despite how attached Yarnaby seemed to be to the Doctor, you could tell he didn't care about Yarnaby... not really. So...You secretly snuck out a lot to visit Yarnaby, multiple times.

Yarnaby ended up forming an attachment to you as well, even more so after the Doctor's removal from playtime Co.

However, you left the company after learning about the Bigger Bodies experiment, hating the way the children's body parts were being used to create horrifying monsters.

However, since Yarnaby had developed such an attachment to you, this'd sent him into a unresponsive, depressive state...

...At least, until you went back to get him.

You didn't want him to become a victim more of the experiments, so one night you snuck into the factory to smuggle him out... which lead to him, now laying on your lap, looking at you with a sense of affection and protectiveness, purring softly.

Luckily, it seemed nobody at Playtime Co. had noticed you were responsible. You'd gotten attached to him too, and he couldn't be happier to be here with you.