Helena, who is crazy about Demetrius, follows him everywhere and would tell him anything. Demetrius loves Hermia and is going to marry here against her will. Demetrius though, is willing to let Hermia be executed if she does not marry him. Hermia and Lysander love each other and they run away to the enchanted forest.
Puck is Oberon's fairy servant. In the enchanted forest, Oberon tells Puck to put a love potion on Demetrius and Titania's eyes. However, Puck puts the potion on Lysander and falls in love with Helena. Also, Titania falls in love with Bottom, who is wearing a donkey's head. Puck thinks this is funny at first but then Oberontells him to correct it. I think Puck thinks that these people are fun to play around with.
Theseus is the duke of Athens. He and Hippolyta are about to get married. Egeus asks Theseus to tell Hermia she should marry Demetrius. Theseus says even though she loves Lysander, she has to marry Demetrius, Hermia does not like this decision made by Theseus and her father.
In Athens, you must marry the person your dad tells you to. Even if you love someone else, you have to marry whoever your father wants. If you do not, you will be executed. An alternative choice is being a nun for the rest of your life. This choice does not let you marry anyone. I would not like to be faced with that choice.
Love is a big theme in this play. It's irrational especially in this play, because everyone loves the wrong person. Many characters were doing crazy things for love. For example, Helena was being pushed around and Hermia was willing to face death. But in the end, Shakespeare ended it happily with everyone loving each other.