For the first time, early in season five, one principal character had finally gotten a surname. Dana (Kimberly Williams) married Dr. Ryan Gibson (Mitch Rouse), and became Dana Gibson. The rest of the principal characters still had no surname.
In season six, episode thirteen, "The At-Bat", the "grown up Kyle" is played by Jim Belushi's real-life son Robert. Also the "mean girl on the bike" at the game, is his real-life daughter, Jamison. Both appeared in the show before.