The joys of parenthood.
I was shocked, appalled, and thrilled to hear my then-two-year-old son sigh, shake his head, and mutter "Shit..." when he made a mistake (in his opinion) coloring his coloring book.
Idiomatic, semantically-correct use of a conditional interjection? At the age of two! What a kid!
(On reflection, it turns out that this particular style of swearing is more his mother's... particularly the sigh and head-shaking.)