For my records, I took down all three of the cats' weights. They are about where they were when I went on vacation in March and switched them to adult food. Spook is right around 12.5 pounds, both when he sat calmly on the scale and when I held him and weighed him. Boo is 8 pounds. Wizard is likely 12.75 pounds. I weighed Wizard 5 times on the scale by himself. Every. Single. Time it registered as 2.5 pounds. These weren't consecutive measurements - I weighed other stuff in between to verify the scales accuracy. And he was sitting calming, just as the other two did, so I don't think he was balancing on the floor. The even weirder part is that 5 out of the 7 times that I weighed him with me, we weighed nine or eleven pounds LESS than I do alone without the cat. This isn't the first time that this has happened with Wizo either. His entire life (I've had him 3.5 years now), it has been difficult to get a weight for him as I always seem to weigh 10 pounds less than normal when I'm holding him. The two normal looking weights for me holding Wizo would peg him at 12.5 and 13 pounds. So I'll just say he's 12.75. I know he is marginally heavier than Spook.
(I just wish the weight loss from picking up Wizo was permanent. :) )