Jenna mentions that she met Jayden 20 years ago. The scene then flashes back to Jenna getting dissed by a young Jayden. The costume she is wearing is essentially the same costume that Jane Krakowski wore 20 years previously in the Broadway musical "Starlight Express." In addition, Jayden is dressed as a street urchin because the young boy playing the urchin Gavroche in "Les Misérables" on Broadway was also providing the voice of Control in "Starlight Express" alongside Krakowski.
One of the people on the train who turns away from Jack during his plea for help finding the right train is Moonvest, who was seen in The Head and the Hair (2007)
Kathy Geiss' audition is likely a reference to Susan Boyle's appearance on "Britain's Got Talent" earlier that year. Boyle, also plain-looking and dressed in frumpy clothes, blew the audience away with her performance of "I Dreamed A Dream".
Frank's trucker hat says "Because".