Heather Elizabeth Morris was 5 months pregnant with her first son. You can clearly see her baby bump when she walks across the glee club room.
When Britney breaks up with Sam, she says "sorry not sorry". That is also the name of the book by Naya Rivera (Santana on the show) published on 2016.
The Supreme Court decision Blaine references won't actually be handed down for another 2 years.
Kurt is the only person in show circle that Brittany doesn't mention or address when comparing everyone to family members.