Question

Why does Shakespeare include Mercutio’s teasing words?

to explain the history of the feuding families
to criticize Romeo’s neglect of his duties
to condemn the established ritual of sword fighting
to contrast the seriousness of Tybalt’s challenge

Answer 1

to contrast the seriousness of Tybalt’s challenge

Mercutio’s mockery and wordplay lightens the scene and highlights the difference between his joking attitude and Tybalt’s deadly seriousness, which helps escalate the tension that leads to the duel.