Weird stuff going on here, needs some input

Ok, here's the problem: I have a dummy unit casting a spell based off of "howl of terror", and when given the order and the spell and such, it casts it perfectly. Here's the thing, I gave the ability I want the dummy to cast to the unit it's supposed to "originate" from as well as the dummy, neglecting to create a dummy ability for the original caster. The ability I gave them both costs 65 mana, and the dummy has a max mana of 1. Regardless, he casts it perfectly. Now that kinda weirded me out. How the hell did it do that? Any thoughts? Anyone?

I've seen that bug happen before, I had this Everquest Team Survival map a long time ago where a charm ability had a 200 mana cost, but when casted, the caster would lose no mana and there would be no cooldown. I don't have a clue on how that happened, however.

I just find it very odd. There's no reason why it would happen, and it isn't a random occurrence, it happens every 30 secs on 6 units on my map.