While Marshall is visiting his mother in Minnesota, his brother Marcus is there. In episode 4 of this season, when Marshall and Lily are trying to decide who should care for their children if they both die, it is established that Marcus had abandoned his family to become a bartender in some tropical location.
The scene where Marshall gets dropped off at the Minnesota airport was actually filmed in PDX. The backdrop shows the sky bridge between the parking garage and the departure terminal, and the close-in scene where Marshall talks with his brother reveals the carts that are at the PDX airport.
Keegan-Michael Key (guy at restaurant) and Cobie Smulders (Robin) would later go on to play a married couple in Friends from College (2017).
Robin's locket is an allusion to the gold watch in Pulp Fiction.