This story comes from the story of Rama told by Tulsidas:
One day Kaushalya left Rama in his cradle and went to offer prayers. She was amazed to find Rama there, eagerly eating the puja sweets! "How can he be both here and there?" she wondered.
As she stared, Rama displayed his cosmic form: infinite beings, millions of universes contained in every part of his body. All of time, all of existence radiated from him.
Kaushalya bowed her head. "O Lord, I beg you to let me forget you have shown me here."
So Kaushalya forgot, and in obedience to his mother Rama never revealed his true form to her again.
This is a popular folktale about Rama's childhood:
When Sita came to Ayodhya, Rama's mother, Queen Kaushalya, was eager to tell her all about Rama.
One day Sita asked, "Rama belongs to the Solar Dynasty of kings that descend from the Surya, the sun-god, but you call him Ramachandra, Moon-Rama. Why is that?"
"Rama wanted the moon to sleep beside him," Kaushalya explained. "But no matter how loudly he called to the moon, it stayed up in the sky. So we put a pot of water on his bed, with the moon reflected in the water. Little Rama slept with the moon, and so we called him Ramachandra."
This popular story is found in the Telugu Ramayana of south India:
The monkeys and bears hurried to build the bridge, dragging huge trees and enormous rocks to the seashore.
The squirrel wanted to help too. He rolled in the sand, ran to the bridge, and shook the sand out of his fur. Again and again.
Then an angry monkey kicked the squirrel out of the way, shouting, "We need real workers!"
But Rama rebuked the monkey. "The squirrel's work matters," explained Rama. "All that sand fills the gaps between the stones."
In gratitude, Rama ran his fingers over the squirrel's back.
That is why the squirrels of India today have stripes.
This legend is popular in Bengal:
To prepare for war, Rama honored Durga, the warrior-goddess."I will offer her 108 perfect blue lotuses," Rama said, "one for each of her sacred names."
So Rama gathered the lotuses and began chanting the names, offering one lotus for each name.
But when Rama reached the last name, he realized he had miscounted: he was short one lotus. Without hesitating, Rama took an arrow, ready to extract one of his eyes to offer instead.
At just that moment, the goddess appeared. "Stop!" she said. "Your offering is complete, Lotus-Eyed Rama." Then the goddess blessed Rama, bestowing victory upon him.
This legend also comes from Bengal:
Ravana's son Virabahu was devoted to Vishnu. Seeing Rama in battle, he recognized Rama as Vishnu on earth.
"O God!" shouted Virabahu, bowing down before Rama. "I am yours! Let your sword send me to heaven." Then he offered his neck to Rama's sword.
"I cannot kill someone who shows such devotion," Rama said.
"Then I will make you kill me," shouted Virabahu, and he launched an attack. They fought violently, until finally Rama's sword cut off Virabahu's head.
The head's mouth kept chanting the name of Rama.
Rama bent down and touched the head, and Virabahu ascended to heaven.
This legend comes from the last (and controversial) book of Valmiki's Ramayana:
After sending Sita away, everyone expected Rama to remarry.
"Who will be his bride?" the people wondered. "Perhaps someone from Ayodhya!" said some. "Perhaps a princess from the south!" said others. "Or the north!" "Or the west!" "Or the east!" "A princess from a nearby kingdom!" "A princess from far away!"
But Rama refused to remarry.
His priests protested. "You must have a queen! You cannot conduct the royal rituals without a queen by your side."
"Sita is still my queen," said Rama.
So he had a golden statue made of Sita, and he kept the statue at his side.
This is a Jain legend about Rama:
After Lakshmana's death, Rama went to the river every day and wept for his brother.
A monk also came to the river daily. Rama saw the monk fill his watering can and then pour the water over a large rock. The monk did this every day.
"That rock is not a plant," Rama told him. "It cannot grow or produce fruit. So why do you water the rock?"
"And why do you shed tears for your brother?" replied the monk.
Rama then understood that his weeping served no more purpose than watering a rock, and he set his grief aside.
Author's Notes:
Baby Rama's Cosmic Form. Baby Krishna makes a similar revelation to his foster-mother Yashoda, who sees the cosmic manifestation of Krishna when she looks inside the baby's mouth. Vishnu's cosmic form is called Vishvarupa, All-Form. More information.
Moon-Rama, Ramachandra. Other legends explain the name differently, saying that Rama's treatment of Shurpanakha and also of Sita put a blemish on his solar reputation, making him Ramachandra. More information.
Rama and the Squirrel. There are other legends about Rama and animal aetiologies, like how the goose got its long neck. More information.
Rama Worships Durga. This story is told in connection with the ritual called Akal Bodhon. More information.
Ravana's Son, Virabahu. Devdutt Pattanaik explains the ending as follows: "This is an example of viparit-bhakti, reverse devotion, displaying devotion by mocking and taunting God.". More information.
The Statue. In another legend, Rama makes a new golden statue for every ritual, and all those statues then become the gopi lovers of Krishna in Vishnu's next incarnation. More information.
The Monk's Rock. When Lakshmana disturbed Rama after being expressly ordered that no one should disturb him under penalty of death, Rama had to sentence Lakshmana to death. Obedient to Rama's command, Lakshmana went to the river and killed himself there. More information.
Image Information:
Baby Rama's Cosmic Form. Vishvarupa at Wikimedia.
Moon-Rama, Ramachandra. Illustration found at Pinterest.
Rama and the Squirrel. Indian palm squirrel in Bengaluru from Wikimedia.
Rama Worships Durga. Akal Bodhan image found at Twitter; see thread for more images.
Ravana's Son, Virabahu. Warriors fighting with swords at Weapons of the Era website.
The Statue. Rama, the statue, and the twins, found at Pinterest.
The Monk's Rock. The Sarayu river, from Expeditions India.