When Twelfth Night was first performed in 1602, it proved to be very popular. Shakespeare's audiences especially took a liking to Malvolio and all of the comedy surrounding his characterization. In fact, Malvolio was so popular that by 1623 Shakespeare's fans came to call the play simply Malvolio. The prank Maria pulls on Malvolio is certainly the height of comedy, especially convincing him to do the things Olivia detests, such as wearing yellow stockings, appearing cross-gartered and smiling, as signs that he is returning her affection, as we see Maria explain in her speech:
[H]e will come to her in yellow stockings, and 'tis a colour she abhors, and crossgartered, a fashion she detests; and he will smile upon her, which will now be so unsuitable to her disposition, being addicted to melancholy as she is. (II.v.179-84)
However, beyond Malvolio, Twelfth Night delves into intriguing themes, such as "conflicts of power, class structure, and sexuality," particularly the sexual complications demonstrated by the fact that Olivia falls in love with who is essentially a fellow woman and even that Antonio, the sea captain who rescued Sebastian, has such strong feelings for Sebastian that his feelings lead him to danger ("Twelfth Night In Performance"). It's these themes that have made Twelfth Night popular throughout the ages, each era wanting to interpret the play differently. In addition, naturally the mistaken identities and mixed-up lovers add to the play's humor, making it one of the most frequently performed plays.