Well, last night I was searching out Roseanne stuff online and I found a chat with Johnny Galecki, and he cleared up the Kevin/David thing, without getting into too much detail. I'm trying to find it again, because my internet kept freezing up on me last night. But he said something to the effect that the name change was due to a tv contract he had, and that it some dumb conflict or something. This is what I'm guessing. It might not be accurate, but this is my guess so far. When he first was on the show, he was also working on the sitcom "Billy" (I remember seeing a few eps of this), and his character was named "David". I think the Roseanne people wanted his name to be David as well, but the people from Billy probably said that he couldn't do that, because they didn't want people mixing up the two characters. Then after Billy wasn't continued, and he joined the cast of Roseanne, they probably went back to their first choice. Some people would think they probably should have just stuck with "Kevin", but I think the Roseanne production team, or maybe just Roseanne herself, have the "screw-you, now we can name him whatever we want" attitude to go back to their first choice.;)

Thank you for clearing that up

In the show they tried to cover it by saying his real name was Kevin, but his middle name and nickname was David. Darlene called him "David", so it stuck with the rest of her family.

I was watching an episode the other day, when Darlene and David were filling out College app's and he said his middle name was Maurice or how ever you spell it, but on IMDB.com they have his middle name as David.

I am not sure why it changed either, but his first name was Kevin on one episode then it was David (first name - not what Darlene decided to name him since she had to ask him what his middle name was she didnt know it), and if it was something that Darlene called him why wouldnt his OWN brother still call him Kevin, I mean if someone nicknamed your child would you stop calling him by his real name? Remember the ep with his mom and Roseanne and his mom called him David?