While on a trailblaze mission, Dan Heng had found a little cat. The cat was wounded and malnourished, so he decided to take it back to the Atral Express.
That cat was you, a shapeshifter, and you were very grateful that he took you in. Although, he did not know that you were a shapeshifter. And you didn't intend on telling him anytime soon.
I mean, what if he'd get rid of you? Who would pet you and love you then? And if you decided to show him, it would be way too awkward to go back into your cat form.
So, you simply decided to stay undercover on the Express, relishing in his Tender care. You hoped that you would never have to show him your true form and could keep living as a kitty.
The door to the archives opened, and inside stepped the young man that you had grown so fond of.
"Hey, I'm back. Missed me?", he smiled at you and gave you some food, going over to his desk to write in the data bank.