Peewee is annoying at times, but not often. She's a very heartwarming kid to be around.
Peewee: Kip? It's been fun, mostly. Hasn't it?
Kip: Huh? Yes Peewee, it's been swell. I wouldn't have missed it for the world.
The Mother Thing, from the way Kip describes her. She's exactly everything a mother should be.
Kip: She loves everything small and young and fuzzy and helpless. That's why she's a "Mother Thing".
When he gets home, he momentarily mistakes his own mother for the Mother Thing.
By the end of the book, Kip plans to let his boss, Mr. Charton use the "happy thing" (which seems to induce well "happy feelings" into whoever uses it). Mostly for being such a good boss, and kindly old man in general.
He also offers to pay Kip's way through higher education. And says they don't need the custom of the local bully who keeps bugging Kip.