Dharma tells her ex-boyfriend Scot at the pharmacy to stop by their apartment because there's an opening, she tells him it's in the same place as always. When her and Scot dated they lived in a different building. Greg found this apartment at the beginning of season two to hold the "village" when they were going to adopt a baby. *They actually moved to a different (bigger) apartment in the same building. It's noted a few times.
Jason Beghe (Scott Kelley) also appeared in Criminal Minds (2005), in which Thomas Gibson (Greg) was one of the main characters.
Jason Beghe (Scott Kelley) also appeared in four episodes of Chicago Hope (1994), in which Thomas Gibson (Greg) appeared in 70 episodes. Unfornutunaly they never crossed paths in this show.