Adel's Laughing Song from Die Fledermaus 

Die Fledermaus (The Bat) is an operetta composed by Johann Strauss II to a German libretto by Karl Haffner and Richard Genée.

Act 2: A summer house in the Villa Orlovsky

Falke, with Prince Orlofsky's permission, is orchestrating the ball as a way of getting revenge on Eisenstein. The past winter, Eisenstein had abandoned a drunken Falke dressed as a bat in the center of the town, exposing him to ridicule the next day. Scheming, Falke has invited Frank, Adele, and Rosalinde to the ball as well. The following pretend to be someone else (Rosalinde acts as  a countess, Eisenstein pretends to be "Marquis Renard," Frank is " Chevalier Chagrin," and Adele pretends she is a upscale actress).

At the ball, the Marquis welcomes his guests. Eisenstein is introduced to Adele, but suspects whom she really is because of her likeness to his maid. Adelle really is the maid but is pretending to get even with her boss-Eisenstein and tease him. This is Adel's laughing song.

 Au Guarda Sorella (Act 1-Cosi Fan Tutte) 

Così fan tutte, ossia La scuola degli amanti (The School For Lovers) K. 588, is an opera buffa by Wolfgang Amadeus Mozart. The libretto was written by Lorenzo Da Ponte.

The title, Così fan tutte, means "Women are like that".
ACT I. Naples, late 1700s. Early morning. Don Alfonso, a cynical old bachelor, says women are not constant in love. He debates this with Ferrando and Guglielmo, young officers who insist their sweethearts -- the sisters Dorabella and Fiordiligi -- are faithful. Alfonso bets in one day he can prove women are fickle when int comes to men.

Fiordiligi and Dorabella are comparing pictures of their boyfriends when Alfonso pays them a visit (thus the song "Au Guarda Sorella")

 La Wally (Act 1-
Ebben? Ne Andrò Lontana

The opera La Wally is best known for this operatic aria: "Ebben? Ne andrò lontana", Act I, sung when Wally decides to leave her home forever.

The opera also features Wally as the heroine who throws herself into an avalanche by the end of the opera.