I had a slight argument with my DM and another player a few weeks ago when we were playing a modified version of D&D 4th. My wizard(-ish) character attacked another PC with a spell (specifically phantasmal force) while under mind control(sort of) and when I hit him the DM said that the other guy should make a will save. I said that doing so would not make sense because I had already rolled against his Will in the attack roll and succeeded.
They argued that saving throws are made when a PC (but not an NPC) is attacked by a spell and if the save succeeds then the effect is negated. This really does not make sense to me. Now, this very case eventually got resolved without halting the game too much but I would like to know in case the question pops up again.