Caplan added, "Yeah, David was still kind of in the life of the show, certainly living through the kids, and we sort of had to deal with it. We made an initial approach to Johnny to see if he was available, but he's sort of not engaging with the business at the moment. But we still felt that to tell a good story about Mark and Ben, we needed the ghost of David in the show."
Considering that the major focus of the finale was Mark's graduation, one might have suspected that David would show up to support his son. However, the lesson in the finale is that Ben (Jay R. Ferguson) is actually a great father figure to Mark. This is a great way to not only acknowledge David, but to also provide an in-universe explanation for his absence — Mark would rather have Ben at his graduation as opposed to his biological father.
As mentioned earlier, though, Johnny Galecki would have been welcome back on the set of "The Conners," but the actor himself is taking a break from acting. Considering that Galecki has been in the entertainment industry for years, a little rest and relaxation is probably great for his well-being, especially when one realizes that Galecki was pulling double duty appearing on "Roseanne" and "The Conners" at the same time he was starring on "The Big Bang Theory." Still, its a shame David didn't pop up in this particular episode of "The Conners," but it makes sense for Galecki personally, and the missing character helped provide a touching moment between Mark and Ben.
