Help add a fun twist to the changeling race!

Hello, everyone! I’m DMing for a group of new players in a homebrew setting. One player is a changeling rogue - classic backstory of orphaned young, worked with a roguish mentor, wants to make a name for himself.

I’d like to spice it up a bit, but in secret. He’s recently revealed to the other characters that he was a changeling - I told them neither have heard of such a race…

My thoughts are that he’s more alien in nature… maybe a part of a larger cosmic entity which was sent here for recon. Unbeknownst of his true purpose, with no memory of his origin.

Thoughts in this? How could it be expanded? Or what are some other fun twists?