And all I can remember is a small exchange he had with him mom in it..
Oncie's Mom: Now, how did you come up with the idea for those silly old Thneeds?
Once-ler: I don't know...
Oncie's Mom: But they're going to ask!
Once-ler: I dunno, I guess I just..... Kept an open mind.
Oncie's Mom: .... An open mind? *Confusedplz*
Once-ler: Yeah, I didn't think you knew the meaning of that, mom. It's okay