The 10k runner who exclaims "I'm peeing!" Is the director of the episode (as well as movies such as Wet Hot American Summer and Role Models) David Wain.
When Winston is scolding everyone in the apartment when he does his "Theodore K Mullens" character, you can see one of Nick's girlfriend break character and start to laugh.
Nick breaks the phone which he had received in the previous episode where he says he is a person without a phone
You can see the yellow shirt "I am Claire", seen in earlier episodes
Bear Hunt: Nick yells Bears when Schmidt is teaching him how to talk to girls and he asks him what happened to his phone.