How Did That Happen?

I was going through my collection of unbuilt kits the other day, looking for something fun to work on, and realized that somehow I had ended up with three 1/72nd scale Challenger I tank models. How did this happen? I don't even really like the Challenger all that much! I mean, it's a fine main battle tank and the British have no reason to be ashamed of it, but it's just not my favorite model. So how did I end up with three Challengers? I have no idea. I blame a twitchy mouse hand when I visit the Squadron on-line catalog, myself.