In the scene where Barney, Ted, Marshall and Stuart are eating steaks after the strip, at the wall of the restaurant there are caricatures of celebrities. Among them, there are caricatures of HIMYM's creators and writers.
Grandma Lois (K Callan) portrayed Martha Kent in Lois and Clark: The New Adventures of Superman through its entire run.
In the flashback where Barney goes to San Francisco, he tells the cabbie to take him to Newark airport. New Yorkers would take JFK or LaGuardia.