Act 2 Sc. 1, Lines 33–41 How does Mercutio’s dialogue in this scene add to your impression of his character?

Mercutio, Romeo's loyal friend, is also something of a foil to our hero. He acts as a mirror to Romeo, highlighting his myriad character traits. In this particular piece of dialogue, Mercutio's vulgar, bawdy, almost juvenile understanding of love stands in stark contrast to Romeo's hopelessly romantic outlook. When it comes to the question of love, Mercutio is both a cynic and a skeptic—very different to Romeo.
Mercutio's idea of love is not dissimilar to that of an adolescent boy. To put it bluntly, love for him is synonymous with sex. So according to Mercutio, Romeo's love is without a target as he cannot be with his beloved Juliet and therefore cannot have sex with her. If only she could be here, muses Mercutio, it would all be so very different:

If love be blind, love cannot hit the mark.
Now will he sit under a medlar tree,
And wish his mistress were that kind of fruit

         As maids call medlars, when they laugh alone. (Act II Scene I).A medlar is a fruit which appeared to the Elizabethans to have a shape resembling a very private part of a lady's anatomy. Mercutio's use of the term shows how immature he can be when it comes to matters of love.
       O, Romeo, that she were, O that she were
        An open-arse, thou a pop’rin pear!"Open-arse" shows that Mercutio's one-track mind is still very much in the gutter. And his use of a puerile pun ("pop her in") merely confirms this. Mercutio's parody of the vocative ("O, Romeo...O that she were...") expresses his fun side as well as his cynical contempt for the conventions of courtly love. The vocative is used by Romeo and Juliet as star-crossed lovers to address each other. Mercutio, however, mercilessly pokes fun at the convention, bringing it crashing down to earth to play in the gutter along with his dirty thoughts.