Pre-Spitfire. Wally makes some snarky comment during training which genuinely offends Artemis. Wally instantly regrets his offense but the damage is already done and he doesn't know how to apologize to the infuriating Archer without damaging his ego.
-Phht. I don't know, just some Spitfire feels 'cause I love them so
Artemis and KidFlash belong to DC