Name's the Same/Theatre


 * The Medium and Sweeney Todd: The Demon Barber of Fleet Street both have a boy Woobie called Toby assisting the not-so-nice principal female character.
 * Vanities is the name of a series (1923-1940) of musical revues by Earl Carroll, a 1976 play by Jack Heifner, and a 2000's musical adaptation of the latter.
 * The Bock and Harnick musicals Tenderloin and She Loves Me have unrelated songs titled "Dear Friend."
 * No, Titanic: The Musical is not based on the film, in fact it predates it.
 * Of course, as the Titanic was an actual ship, there are many books, paintings, etc. titled after it.