One time, there was a beautiful woman named Anjana. While she was walking in the forest, she saw a monkey meditating under a tree. Upon seeing it, she started laughing. She didn't realize that the monkey was a sage in disguise. The sage became angry and cursed her that she would get the face of a monkey. 

She cried and begged for forgiveness. The sage was moved and decided to lessen the curse - he asked her to pray to Lord Shiva and give birth to Shiva's incarnation. When that happens, her face would return to human. But her son would get a monkey face in her place.

After a few years, she ran into the King of Monkeys and fell in love with him. Both of them decided to get married. She remembered the sage's words and decided to pray to Lord Shiva, asking for a child.

Far away, the King of Ayodhya was hosting a grand prayer, requesting the Gods to bless his wife with children. The priest gave each of his wifes some magical kheer pudding to eat but a bird ran off with some of the pudding. The bird dropped the pudding into Anjana's lap while she was praying. Anjana ate it and was blessed with a child. As the sage had predicted, the child was born with a monkey face. He was named Hanuman.