cutie pants

A term of endearment, usually expressed as a sudden exclamation over a child & not primarily related to looks or appearance, but rather the overall sweetness of the child a combination of behaviors, acts or expressions. Sometimes used when a child does something sweet, but unexpected or surprising. This colloquial phrase expresses the feeling of delight over the child's cuteness by the person making the exclamation. Sometimes expressed (but rarely) over teens or young adults. An American colloquialism.

What a little cutie pants!