Die Fledermaus (literally, Batman) is an operetta by Johann "The Other" Strauss, which exactly follows the plot of La Rondine, which, as you may recall, has the same plot as La Traviata, which, as we all know, is really just the same story as Pretty Woman.
Let me sum up the plots of both Die Fledermaus and La Rondine for you quickly. Act 1: Rich people sit around at home before eventually deciding to all go out drinking, separately, and in disguise. Act 2: Everyone is pretending to be someone else and drinking heavily, the chambermaid is wearing her bosses dress, and they mostly recognize each other, but pretend not to. Act 3: We get to see what happens to everyone after one night of major drinking and bad decisions.
So as you can see, they are basically the same show, except that many of the characters' names are different, and they say and do different things, and also one is about a bird and one is about a bat.
The story of Die Fledermaus opens with our hero, Eisenstein, being badly mistreated, in that there is another tenor on stage, singing to his wife. If there is one thing a tenor hates, it is another tenor on stage singing, so Eisenstein comes stomping home, where we learn that he has a terrible lawyer, and must now go to jail. Luckily, his friend Falke comes along and tells him about a great party, so Eisenstein naturally decides to put off going to jail, as there will be an open bar at this party.
Now, some other people are going to the party as well, and if they were tenors I would tell you about them, but as they are not, let's skip to the part where Eisenstein shows up. He is very happy, because the other tenor has now been arrested, and, as such, cannot participate in Act 2. Eisenstein starts looking around for girls to show off his watch to, because back in those days watches were apparently a potent aphrodisiac. Unfortunately for him, his wife is at the party as well, and even more unfortunately, she tricks him and steals his watch. Having nothing else to woo girls with, he decides to end the act and go to jail, where, unbeknownst to him, his arch enemy, the other tenor, is waiting.
Act 3 is mostly a gigantic duel between the two tenors, similar to that battle between Qui Gon Jinn and Darth Maul at the end of The Phantom Menace, except that instead of having to race through corridors and use the force, Eisenstein has to dress up as a lawyer and yell a lot. It's hard to tell if the show ends as a comedy or a tragedy, since our hero does end up in jail. But he also gets his watch back, so I guess it all evens out. The real tragedy is that nothing really bad happens to the other tenor, but I suppose we can only imagine that horrible things happen to him after the curtain comes down.
Thus ends the tale of Mr. Eisenstein, the dashing and brilliant hero of our story. And if you want to know stuff about the other characters, well, go see the show.