Nicholas was Zurg (from Toy Story).
Cecilia was a homemade bee (melt your heart moment, while I was making her costume she hugged me and said "you're the bestest mom ever, making me a costume instead of just buying it)... she wanted to be a bee because "I want to get back at all those stupid bees that sting me". Love that seven year old's logic. (Antenna and wings from the 99c store)
Abigail was a witch - she used last year's costume again, we just added a pair of witch costume pants underneath to make it a little longer.
Sabrina was a "vampire fairy".
Nathanial was the "candy cop" and spent the evening handing out candy to all of the trick or treaters... after setting up speakers, a strobe light, a black light, and a fog machine. Our house was a hit.