Because, really, is there ever such a thing at the Weasley house?
"Lily Evans," He began pompously, before smiling hopefully at Lily's amused face. Noticing that, James' smile got even wider, "May I have this dance?" Rolling her eyes, Lily nodded her ascent, as she stood and took his hand.
It takes a bad day to make Lily realize that maybe she did misjudge James Potter. Oneshot. JP/LE.