There is a short flashback, Marshall and Ted are seen eating a sandwich while watching a Kung Fu-movie. This references How I Met Your Mother: How I Met Everyone Else (2007) in which older Ted replaces all references to smoking marijuana by describing that he and his friends were eating a sandwich.
The trivia item below may give away important plot points.
Three to five years later' when Marshall is carving the turkey with a lightsaber, his mom isn't in shot, but is mentioned as being there. His dad, however, isn't in shot nor is he mentioned, possibly foreshadowing his death 2 years later.