Continuity mistake: Before the party scene, there's a little musical montage where all the occurs can be seen getting dressed. There's quick second long shot of Lord Goring, played by Rupert Everett, placing a bright red flower in his buttonhole. A few seconds later, he's placing a white flower in his button hole. Its really quick but it unmistakably Lord Goring.
Trivia: The play that all are watching when Lord Goring fools around with his looking glass and Gertrude asks Robert what his business with Mrs. Cheevley is, is "The Importance Of Being Earnest" by Oscar Wilde. In the end you see the author coming out on the stage and saying a few funny words. This really occurred at the premier, Oscar Wilde did really say these things. It is a kind of play in a play, as "An Ideal Husband" was also written by Wilde.