[Honestly, the Once-ler is sort of baffled at first. He hadn't really expected anyone to miss him or be sad he was gone, except for maybe Regina. The fact that a kid was actually sad they missed the chance to say goodbye is so weird to him, but...he's touched.

He crouches down with Boris in his arms, so he can be on Mabel's level.]

Uh. ...Sorry about that. I definitely wouldn't've left if I could've avoided it. This place is loads better than where I'm from, but...I'm glad I got to see you again?

[She's a sweet girl, and he doesn't want to make her sad.]