I know that the popular portrayal of Teddy Lupin is that of a cocky punk rocker-type kid, but what about a Teddy Lupin who has a strong need to be What Is Expected, instead? Not someone who likes to stand out in a crowd or who feels any real need to rebel, but someone who grew up in an atmosphere of grief-tinged determination and internalized it, the kind of child who looked at the adults around him and thought “I’m going to make it as easy for them to love me as I can”?
Maybe when he’s around his grandparents he picks up Tonks’ nose and laugh and penchant for cotton-candy-colored hair, and when he’s around Harry he adopts Lupin’s slouch and crooked half-smile and heavy-lidded eyes. Maybe when they go out in public—in front of the Wizarding public, I mean—he’s bright colors and bright laughs and easy with the fame, whether he really feels comfortable with all those eyes on him or not, because he knows it’s part and parcel of being Harry Potter’s godson and the child of fallen war heroes, and the last thing he’d ever want is to make his family think he’s uncomfortable with them. Maybe when they go out into the Muggle world—to awkwardly shake hands with Petunia and Dudley, to visit Ted Tonks’ extended family, to meet Hermione’s parents—his hair still looks colored but now it looks painted or dyed, not like it naturally grew out blue and green and pink, and if his face still changes nobody can tell, because by the time a muggle looks back a second time it looks the same as it was before.
I dunno, I just feel like the child of a war like that would know the value of being what is needed, what is expected, what is easy and advantageous. So he makes adjustments to his appearance and mannerisms on the fly based on the reactions of those around him, smooths out the rough patches and makes everyone more comfortable than they would have been otherwise, not because he thinks he owes it to anyone but just because he recognizes that it’s better than the alternative. Probably there’s enough upset in his life without him manufacturing his own.