When Dr. Spaceman (Chris Parnell) is escorted from the doctor's office in the opening sequence, he turns to Liz Lemon and yells, "Hey, that's a series wrap on Leo Spaceman, suckers!" And, of course, it was.
When Jack says that Jenna's genetic test shows she has an extra Y chromosome, this means that Jenna is genetically intersex, with XXY chromosomes.
When Hank Hooper says that when he turned 21 he had his first white child. This may be a reference to the fact that Ken Howard, who plays Hooper, famously played Thomas Jefferson who fathered black children.