One can actually argue that both Puck and Bottom are equally important in A Midsummer Night's Dream. Some literary critics even argue that both characters play the role of the fool. Shakespeare's fools are always known for their comedy, but more importantly, they are turn out to be the wisest and most instructive characters of all (Shea). Puck is a more traditional fool because, even though he makes mistakes for the sake of comic effect and plot development, he is also extremely wise in his understanding of human nature. Bottom, on the other hand, is one of the more ridiculous characters, especially with respect to being self-deceived into thinking far too highly of himself. While Bottom says some very wise and theme-important lines, he mostly remains unenlightened by the end of the play. Not only are Puck and Bottom equally important because they are equally fools, they also portray central themes. Puck portrays the theme of mankind's foolish nature, while Bottom embodies the theme of illusions.
One of Shakespeare's central points is to assert how arbitrary love really is and how foolish mankind's behavior is when affected by love. Puck embodies both the arbitrariness and foolishness of love by mixing up the couples and inciting all of the anger and distrust that follows. The dramatic irony resulting from the mix-up is that Helena believes she is being back-stabbed by Hermia while Hermia believes the same of Helena when the reality is that things simply aren't what they seem to be--the switch in affections is due to enchantment. However, since none of the mortals are able to see they have been enchanted and break up friendships because of it, Puck rightly exclaims, "Lord, what fools these mortals be!," which embodies the theme of foolish behavior (III.ii.116).
Bottom, on the hand, makes an insightful comment to Titania, stating she really has no reason to love him, which embodies the theme of the arbitrariness of love. In addition, the mechanicals' play itself that Bottom has a central role in embodies the theme of illusions because all the mechanicals are under the illusion they can perform a magnificent play when the reality is just the opposite. Bottom himself particularly embodies the theme of illusion because he, for no real reason, thinks very highly of his own acting skills and he never awakens from this illusion.
Hence, both Puck and Bottom are equally important in their roles as fools because both embody different central themes.