When the curtain opens on the prologue of Fiddler on the Roof, we see and hear the fiddler playing, and a Title Drop is the very first line in the show. The fiddler, who plays no part in the plot, is explained by Tevye to be a metaphor for the tenacious existence of Anatevka and its people.
The opening scene of Damn Yankees has one Title Drop in dialogue (what Joe says when Meg asks him if the Washington Senators won the game he was watching) and another in the song "Six Months" ("Those damn Yankees! Why can't we beat 'em?")
Lady Bracknell: My nephew, you seem to be displaying signs of triviality. Jack ("Earnest") Worthing: On the contrary, Aunt Augusta, I’ve now realised for the first time in my life the vital Importance of Being Earnest.
"There are no Angels In America" re: the lack of spiritual or ethnic history in the nation's culture—it's a big rant about how everything is political. Although, in the context of this play, there are angels in America, and Louis is, as Belize says "so full of piping hot crap that the mention of [his] name draws flies" in the monologue/monolith in which he makes the above statement.
In the opening scene of The Music Man, one of the salesmen on the train calls Professor Harold Hill a "music man" during the "Rock Island" patter.
In the Musical "Catch Me If You Can", the opening song "Live in Living Color" has a title drop on a high note at the end of the bridge
"What's a name/Just window dressing/Everyone knows that it's the clothes that make the man/Play the game, just keep 'em guessing/mix and match me, try to catch me/If you can!"
Paul Rudnick's I Hate Hamlet does this unabashedly, as the script calls for a lightning strike for emphasis upon delivery of the line.
Les Misérables is generally considered to be an untranslatable title. It is dropped in the finalé in the original French version of the musical; it is translated as "the wretched of the Earth" in the more widely-heard English libretto, but this is a loose translation and loses the effect of the Title Drop.
In Drew Hayden Taylor's Someday, the word "someday" is pronounced exactly twice: at the very beginning of the play, by the mother, Anne, who states that she'll be rich "someday." She wins the lotto and also fulfills her dream of meeting Grace/Janice, her daughter who was taken away by children's aid 35 years earlier. The family reunion seems to be going well until Grace, now the rich lawyer Janice, asks why she was taken away and Anne tells her the truth, that it's because they were Native Canadian and poor. Janice can't accept that answer and realizes how different she is from her birth family, having been raised by an upper-middle-class family while her mother and sister live on reservation. She leaves quite brutally and merely states "I'll be back...someday." This is the most chilling line of the play, especially since it started set up as a play about dreams being fulfilled. Made even more poignant since in the sequel, Only Drunks and Children Tell the Truth, she does come back... for Anne's burial.
Given that the word "Wicked" is spoken often in the 2nd act of the eponymous show, there is one conversation where Elphaba emphasises to Glinda that she is now "the WICKED witch of the west," which is important.
More whimsically: "For the first time, I feel...wicked."
The very first song of the show is 'No One Mourns the Wicked', which ends with the ensemble shouting the title in unison.
Word of god has stated that he originally intended for all the song titles to include some form of "Wicked", "good", "bad" "wonderful", etc. In the end only 6 songs did. ("No One Mourns the Wicked", "Something Bad", "Thank Goodness", "Wonderful", "No Good Deed", & "For Good")
In Up The Down Staircase, the title (an offense one of the protagonist's students is detained for) is rather painfully dropped twice, once near the beginning and once at the play's "climax."
"When he died—- and by the way he died the Death of a Salesman, in his green velvet slippers in the smoker of the New York, New Haven and Hartford, going into Boston—-when he died, hundreds of salesman and buyers were at his funeral. Things were sad on a lotta trains for months after that."
Subverted in Ah, Wilderness! by Eugene O'Neill: the character is interrupted just before getting to that line in a poem.
Arthur Miller's All My Sons: Joe says at the end, "Sure, he was my son. But I think to him they were all my sons. And I guess they were, I guess they were."
"You're a good man, Charlie Brown." Not only the first song, but the last line of the play (said by Lucy, of all people).
The Cole Porter musical Out Of This World drops its title in the song "No Lover."
A Streetcar Named Desire has a literal Title Drop in its first scene, where Blanche tells how she came to the house on Elysian Fields. Later, there is a less literal but more meaningful reference:
Stella: But there are things that happen between a man and a woman in the dark—that sort of making everything else seem—unimportant. Blanche: What you are talking about is brutal desire—just—Desire!—the name of that rattle-trap streetcar that bangs through the Quarter, up one old narrow street and down another...
A double title drop is done in Andrew Lloyd Webber's Tell Me on a Sunday. There's the title song, but it also contains the lyrics "let me down easy, no big song and dance". Tell Me on a Sunday was combined with Variations to form the reworked show Song and Dance, consisting of one "song" act (Tell Me on a Sunday) and one "dance" act (Variations), so this one is a retroactive title drop as well.
Sweet Gay Baby Jesus: Used as an exclamation during the course of the play, rather than a character name, as some had hoped.
In The Cat and the Canary, no cats or canaries are brought up until the second act, when Annabelle starts flipping through a random book and finds herself reading about fear and how to overcome it through understanding:
"Take a bird—a canary in a cage—put it on a table—then let a cat jump up and walk around the cage, glaring at the canary. What happens? The canary, seeing its enemy so close to it, is frightened almost to death. But if it had understanding, it would know that the cat couldn't reach it while it had the protection of the cage. Not knowing this, it suffers a thousand deaths—through fear."
Several characters in Dog Sees God title drop the scene titles, and Beethoven mentions in The Vipers Nest that it's said "a dog sees god in his master." Interestingly, the play also drops the title of another Charlie-Brown themed work in the final monologue, as CB reads a letter from his mysterious pen pal CS (Charles Shultz) who tells him that despite his struggles, he is a good man.
"The sight is dismal, and our affairs from England come too late. The ears are senseless that should give us hearing, to tell him his commandment is fulfilled, that Rosencrantz and Guildenstern Are Dead."
Not a title song, but the last lyric in the musical Ordinary Days: "... the color of an ordinary day."
Reciter: From the personal journal of Commodore Matthew Calbraith Perry. 14 July 1853. As I supervise the final preparations for this afternoon's historic landing at Kanagawa, I am moved to hope the Japanese will voluntarily accept the reasonable and pacific overtures embodied in our friendly letter.