You asked, so here's the scoop!
During the first season in which Dick Sargent took over the role of Darrin (season 6), Samantha gave birth to her second baby, a son they named Adam. In real life, Elizabeth was pregnant with her third child Rebecca. Adam was "born" on 10/16/69, in episode #175 entitled "And Something Makes Four". This first season he was shown as an infant, and to my knowledge, the baby who was used in this season was never credited.
With the start of the 7th season we saw an older, dark haired child who played the part of Adam until the show ended. The Adam character was never really developed very much, though there was an episode built around whether this child was a warlock or a mortal (8th and final season episode #242 "Adam, Warlock or Washout"). It was determined that Adam WAS a warlock, though this episode left many people confused about that fact, since there were parts that were a bit unclear (was it really Maurice that helped Adam along with his powers?)
The child who played the part of Adam was credited as "David Lawrence". In reality, there were 2 twins who played the part, David and his brother Greg. Since I have gotten a lot of questions about what happened to the actors who played this part, I present the following.
The boys gave an interview on a talk show a few years back hosted by Vicki Lawrence. Here they stated that they were the sons of actor Tony Curtis, but that Curtis never would acknowledge them. They now go by the last name of "Mandel" (their adoptive family's name). Hear the full interview here (streaming), and see a video clip from the show here (1.8 MB).
(Bio excerpts below from Herbie Pilato's 1996 book "Bewitched Forever")
David Lawrence (now "David Mandel-Bloch")
Like his twin brother Greg, David is gifted in both art and writing poetry and has attended college on and off. One of David's favorite artistic pastimes is painting Simpsons characters on denim jackets. His past acting credits include the TV movie "Victory at Entebbe" and several commercials for Listerine, Southwestern Bell and Pillsbury. He has always appeared on TV in tandem with his brother! "Who knows," he says. "One of these days I may even return to acting, but for now, I prefer to kick back and experiment with a lot of different careers." Today one of those careers includes being the head chef and kitchen manager for Italy's Little Kitchen in Manhattan Beach, CA. Besides painting, David enjoys skiing, riding motorcycles and skateboarding. His favorite TV shows include MASH, Absolutely Fabulous, COPS and All My Children (the only soap he can stand). David is engaged to Paula Matveld.
Greg Lawrence (now "Greg Mandel")
After trying college, Greg now works as a production assistant for New Wave Entertainment in Burbank, CA which produces trailers for upcoming films, radio and TV spots. He and his wife Teri live in CA with their 5 cats.
Greg and David's mother says that her sons are typical products of the 70's and 80's, and says that she is a parent from the 50's who prefers to see them well-educated, with their feet firmly planted on the path toward responsible and lucrative futures. "Not only are they gorgeous, bright and extremely creative young men, but they are warm, generous, caring and loved by friends and family alike".
