Alan and Ann are clearly suffering from a lack of energy since they put absolutely no effort into their secret identities. They probably decided to be brother and sister so they'd only have to make up one last name.

They also have the subtlty of a brick. Alan tells a group of adoring school girls that he never eats...but that's nothing compared to Ann telling Serena that she doesn't need food, just energy(fortunately, Serena's also been taking her stupid pills and replies, "Oh, you forgot your lunch?")