During the night out on the town to fire Mr. Rumsen, Don's facial hair grows exceedingly fast within a span of 20 minutes.
When Roger Sterling (John Slattery) speaks to Mona Sterling (Talia Balsam) after she leaves Donald Draper's (Jon Hamm's) office, the bottom left button on his suit his unbuttoned. However, when he turns to face Mona leaving the office, all four buttons in his suit are buttoned. [47:04:00]
Sally's arms between shots as she embraces Draper.
As the pool secretaries react to the death of Marilyn Monroe, which happened the day before, Jane tells Draper that Sally called the office last night asking about him. Last night would have been Sunday, 5 August, when the office was closed.
Roger tells Don that rival agency BBDO "hired a colored kid", as if this was something that just recently happened. But BBDO had hired graphic designer George Olden in 1960, two years before the episode is set.