Lucy Hale (Katie) was dating David Henrie (Son) at time of filming this episode
The 'Dirty Dancing' scene is actually the second time Neil Patrick Harris has recreated a scene on television from a Patrick Swayze movie. The first was in Doogie Howser, M.D. (1989) Season 3, Episode 1, where he recreated a scene from Ghost (1990).
When Robin is telling Ted that she can't say 'I love you', she hums the words and signs 'I love you' in ASL
Ted tells his Children that Katie (Lucy Hale) ended up pregnant with quintuplets. Ryan Pinkston who plays Katie's boyfriend Kyle, starred in the Fox show Quintuplets.