The old trick of posting "evidence" to yourself by registered mail, thereby "proving" the date upon which it came into your possession is a legal urban myth, and as a trained and experienced lawyer Goodwin would know that. A number of attempted stings in the 1940s where con-men posted empty envelopes to themselves and later carefully steamed them open to insert the "evidence" meant the technique has no legal standing at all. Goodwin is not attempting a bluff - he is genuinely delighted when he is handed the envelope. [Registered mail is different from a regular mail posting. The post office stamps the envelope or package along the seal of an envelope, to reduce the possibility of tampering. A credibly sealed envelope would be acceptable as evidence in a court of law.]

Dick Goodwin's boss gives him one week in New York to find proof. On the day he meets Charles Van Doren, Van Doren has just appeared on the Today Show where he said that he's been on Twenty-One for 9 weeks. However, by the time Goodwin interviews Herb Stempel; Stempel mentions that Van Doren has been on Twenty-One for 11 weeks. This indicates that Goodwin has been in New York two weeks and would've had to have returned to Washington, D.C. and give up his investigation. [Exactly as it happened in real life - Goodwin had establsihed a lead within a few days and stayed in New York to follow it through.]

The opening sequence of Twenty One is shown twice. The first time, Jack Barry stands at the podium awaiting his cue to begin the show, but the second time, the band strikes up, and after the announcer makes introductions Barry runs to the podium from backstage. [Usually, before start filming TV shows, the lightmen and the producers want to see how the host is seen in the cameras and usually give final instructions. That's what happened in this scene: the producers wanted to see how Barry looks in the camera, and then he did his famous entry.]