When Jess declines a call from Nick on her cell phone, you can briefly spot the infamous "puppy in a cup" picture set as her phone's wallpaper. This is a reference to Season 2 Episode 7, Menzies.
When Winston is describing embarrassing things that have happened to him to Ally, the last thing he says is "I dislocated my thumb getting off a couch." This is based on a true story when Lamorne Morris hurt himself trying to do something funny while filming a scene for the show.