When they're sitting in the diner, a girl in a white hoodie is seen walking to a table behind Lily and sitting down. There's a shot of Ted, and when the camera goes back to Lily, the girl takes her seat again.
When Barney is "taking a leak" after disappearing, he sticks out his head facing North (from the spectators point of view, merely, towards Ted's room). We know that the bathroom is actually facing West (spectator's point of view, again. Opposite the kitchen). Is he peeing on a plant? If so, why does Marshall seems so cool about it?