Theseus won't let Hermia and Lysander be together.
Titania won't give the Indian boy to Oberon.
Puck put the love spell on Lysander instead of Demetrius.
Egeus, Hermia's father, wanted her to marry Demetrius. Hermia wants to be with Lysander. Egeus brought them to Thesues, the Duke of Athens, to decide who Hermia will marry. Theseus decided that Hermia must marry the man of her father's choice or die.
Demetrius fell in love with Helena and didn't want to marry Hermia.
A servant of Titania's had a son but died. Titania promised to protect and take care of the boy in her memory. Oberon wants the boy in exchange for their fighting to stop. Their arguing has caused the seasons to be out of balance.
Oberon took the love spell off Titania and didn't want the boy.
Oberon saw Demetrius and Helena fighting in the woods and told Puck to put the flower with the love spell on Demetrius so they could be happy. They didn't know other people were in the woods so Puck mistook Lysander for Demetrius. When Lysander woke up, he saw Helena and fell in love with her.
Puck took the love spell off Lysander but kept in on Demetrius.
Puck kept the love spell on Demetrius to make everyone happy. After Demetrius explains that he doesn't love Hermia anymore, Theseus decided that everyone can marry who they love at Theseus and Hippolyta's wedding.
Oberon saw how much Titania loved Bottom after putting the love spell on her and got jealous and missed her. He didn't care if he got the Indian boy anymore and wanted to be with Titania again so he took the love spell off and ended their fighting.
After Oberon and Puck noticed that Puck put the love spell on the wrong person, he took the spell off of Lysander so he would love Hermia again. He kept the love spell on Demetrius because of the fighting they had seen earlier between him and Helena.