The character of Mercutio in Shakespeare’s tragedy Romeo and Juliet is a jokester whose barbs are often targeted at one of his closest friends, Romeo.  In particular, he is fond of humoring Romeo regarding the latter’s unrequited love for Rosaline, a member of the Capulet clan, which is at a virtual state of war with Romeo’s clan, the Montagues.  Mercutio, of course, is neither a Montague nor a Capulet, and moves easily between the two factions.  With respect to his jokes at Romeo’s expense, which are said with love, they include his suggestion that Romeo must partake of the festivities at the Capulet mansion wherein a large masked ball is taking place.  In an effort at lifting the smitten Romeo out of his doldrums, Mercutio responds to his friend’s rejection of the suggestion he crash the party by saying “Nay, gentle Romeo, we must have you dance.” 

Later, when mutual friend Benvolio urges Mercutio’s help in locating Romeo, the latter responds by declaring loudly

“Nay, I’ll conjure too. Romeo! humours! madman! passion! lover! Appear thou in the likeness of a sigh!”

Mercutio is, again, making fun of Romeo’s unrequited passion for the elusive Rosaline.  Finally, in greeting the love-stricken Romeo, he refers to his friend in an unflattering but well-intentioned manner as follows:

“Without his roe, like a dried herring: flesh, flesh, how art thou fishified! . . . Signior Romeo, bon jour!"

Mercutio clearly hopes to lift Romeo’s spirits and divert his attention away from Rosaline.  Following rapid banter in which the two spar jokingly, Mercutio feels he has achieved his objective and succeeded in getting Romeo to reengage with society:

“Why, is not this better now than groaning for love? now art thou sociable, now art thou Romeo; . . .”

When, in Act III, Scene 1, Mercutio is killed by Tybalt, who is killed in turn by Romeo, precipitating the fatal events that make Romeo and Juliet the tragedy that it is, one of the play’s great spirits is taken.  Mercutio’s death marks the beginning of the end for Romeo of the Montagues and Juliet of the Capulets.  His death, and Romeo’s reflexive killing of Tybalt, put in motion the chain of events that ends with the lovers’ deaths.