When I saw the post above on Friday morning I was a bit disappointed. I went to Toys R Us to try it anyway, I can be persuasive
I picked up 8 sets of Alien. They still had them on the store floor, luckily. I didn't want to grab them all as it wouldn't help my case if I looked like a total horder.
I took them to the checkout. I took a copy of the flyer with me and showed them where it said ANY set and gave them the Aliens. The girl tried to ring it up, of course it didn't work. She said "I'll be right back, I'll get this sorted out for you". She came back a minute later after talking to the manager and said "I've just got to do the discount for you manually at the end, it's no problem". And it wasn't. She rang up all 8, then deducted 4 of them. Job done!
Another 8 Aliens to join my invasion force! BWHAHAHA!