In the anime, why does Neji's forehead seal disappear sometimes when he's wearing his disguises for Lee's genjutsu/skits? It doesn't seem like an animation error since he usually has it when he's bathing or in his swimsuit, but when he wears a costume it seems to just vanish. It's especially glaring since in some of the earlier episodes, he had it even when in a skit (Nejiko, for example).
Quite possibly offscreen Henge No Jutsu.
Maybe he uses make-up as to not give himself away...