The faeries that are in A Midsummer Night's Dream are not the "Tinkerbell" faeries that most of us grew up with LOL. Puck, one of the main characters, is a faerie and is very mischievous and is a troublemaker! The other faerie that interferes is Oberon, the king of the faeries. I would definitely say they cause complications in the play. Puck likes to cause problems with the couples (all in good fun). He is bawdy and uncouth. The faeries quite frequently caused problems in the mortal world when they had affairs with them and/or interfered with their lives. They also could positively affect people's lives, as well, however. The faeries looked very human and were not very different from them except for the fact they could use magic/spells, etc.
Yes they suely do!
Faeries play a provocative role in AMND, because they occupy the space/time between the rational mind and non-rational mind. In AMND, Shakespeare allows invocation, as in other plays involving magic, like The Tempest;Ariel must pass through Prospero's tests to be freed from his service. Ariel's mind is child-like, fickle, but with a conscience, whose physical identity is made of the myriad substances of the natural world. When he is released from indenture, he returns to the elemental reality of the woodlands, air, and seas. Such is the substance of the faeries in AMND as well, since Oberon, Titania, and all of the others occupy the space unseen by various characters [people from civilization]. Their powers and potions inebriate the lovers and other people; these potions serve a symbolic, yet tangible aspect -- as various animate functions and extensions of naturally-occurring phenomena in the woods. Their roles are provocative because they are real, if you possess the capacity to see them and interact with them. Shakespeare's sources here reveal derivations from Druidic, pagan, and pre-Christian religions as well. Sprites, waifs, and flowers gain personification, involving in people's lives through their visions. These visions are not all hallucinogenic either, because the visions emerge from provoked consciousness, nurtured through the belief, understanding, and acceptance that these beings are indeed palpable entities in the phenomenal world.