Mike Lookinland, who is most famous for playing youngest son Bobby Brady on The Brady Bunch, appears briefly in this episode as the boy on the train who is immediately interested in Mary. Interestingly, Melissa Sue Anderson (Mary) appeared in the 5th and final season of The Brady Bunch as a little girl that kisses Bobby and gives him the mumps.
Reply: Lookinland isn't the only "Brady" connection here. Look quickly for the woman walking her dog outside the hotel in Chicago. That's veteran British character actress Barbara Morrison, a scene-stealer whenever she appeared. She played the drama coach of Greg Brady's girlfriend, Randi, in Season 2's Call Me Irresponsible on The Brady Bunch. Ms. Morrison died of heart failure in California in 1992, at the age of 85.