Act III, scene ii is filled with confusion, all created by Puck, who put an ass’s head on Bottom. After Puck put the magical love juice in Titania's eye, she fell in love with Bottom because he was the first thing she saw when she awoke. Puck also put the love juice in Lysander’s eye, not Demetrius’, by mistake because both boys are wearing "Athenian garments," so Puck assumed that the first male he saw dressed this way (Demetrius) must be Lysander. The conflicts in this scene are due to Puck's mischief. Puck is the personification of "crazy (irrational) love."
Hermia believes that Lysander has been murdered (because he would never have left Hermia alone in the forest) and assumes that Demetrius must have done it. Demetrius, under the spell of Puck's magic love juice, tries to convince Hermia that he loves her more than Lysander. Helena appears, followed by Lysander. She is convinced he is making fun of her with his vows of undying love and is very angry. Their arguing awakens the sleeping Demetrius who also begins to love Helena (the first thing he saw upon awakening after re-receiving the love juice). Helena is sure the two men are just making fun of her to be mean.
Hermia arrives and is told by Lysander that he is now in love with Helena. Helena thinks Hermia is the third party to this joke and threatens to beat Hermia up. The two men leave to fight a duel over Helena. Helena runs away.
Puck tricks them all into falling asleep, then places the love juice again in their eyes. The audience by now is filled with suspense, wondering how the mix up will be resolved.
"What fools these mortals be!" and aren't we encouraged to agree with Puck's sentiments when we see the lovers in action in this scene! It is in this scene that the parody of the lovers reaches its climax - both Lysander and Demetrius are in love with Helena who still loves Demetrius and Hermia still loves Lysander and can't believe that Lysander now loves Hermia. Confused? You should be!
One of the central ironies in this scene is that Lysander, who up until now has been so constant in professing the truth of his love for Hermia, now shows what a shallow and unconstant man he is after one little drop of love potion. His mask of devotion has been exposed and we see him for who he really is. In fact, you might want to think about how this operates for all of the lovers - now they are in the wood and have become the playthings of Puck and Oberon, we see them in a completely different light - and perhaps a truer one.
Of course, the action does expose how irrational we can behave when we are affected by love - even friendship takes second place to pursuing our desires, as is modelled in the amusing cat-fight between Hermia and Lysander. Another central irony (and rather uncomfortable when you think about it) in this passage is that although we enjoy immensely this scene and the lovers' fight, we recognise in their behaviour some of the stupid things we have done for love - how irrational we can be for love - and also, without the help of Puck's magic juice, our affections can change so quickly in the "heat" of love. It is we who are inconstant and fickle and do irrational things under the "spell" of love. Ouch.