Near the end of the Marvelous Marriage scene, at around 57 minutes, Gustav and Jacqueline make their way to the stage. A few moments later, they can be seen sitting at the rear of the theater as the audience cheers.
When Sunny wins in Poker against Count Olaf's henchman, you see that she wins with a Straight Flush (Same suit and consecutive numbers) with an A/K/Q/J/10 of Spades. However, a Jack of Spades is also in the henchman's hand, and there is only one of each card in a traditional 52-card deck.
Justice Strauss declares that the marriage contract is void because Violet signed with her non dominant hand. In reality this would not make a contract void and anyone who has gone to law school would know this.
When you see Klaus and the Judge standing on the stage in front of the chalkboard, you can see the camera that is pointing at the stage.