Shakespeare addresses the role of fate in relationships and tragedy throughout Romeo and Juliet from the Prologue's mention of "star-cross'd lovers" to Romeo's comment about being "Fortune's fool" in Act III, scene I. Romeo's use of the word 'fortune' can be seen as an allusion to Fate, and a fool was like a jester, someone to laugh at at or be amused by. In Act III, scene I in the play when Romeo calls himself "Fortune's fool", he makes an egregious error; Romeo, maddened by grief, kills Tybalt after Mercutio dies from a wound by Tybalt's sword.
The moment is darkly ironic, of which Romeo is well aware with his "Fortune's fool" remark, because he really did not want to shed any Capulet blood; what he really wanted was to mend the rift between the two families through his loving marriage with Juliet. Now he has killed her cousin, Tybalt, and fears that their fragile alliance may shatter upon her knowledge of his deeds. With these thoughts in the back of his mind, Romeo feels as though Fate must be truly laughing at him, and that he is merely a puppet for her amusement and torture.