It seems that an itinerant juggler and mountebank took monastic vows. He was illiterate and had no particular skills, so he worked in the fields and nobody thought much of him. But he had a particular devotion to the Christ Child.
He was in the chapel late at night to pray after his day's work was done. He used to look at the sculpture of the Christ Child in his mother's arms and worry that he looked sad. One night, he decided that he would do something to cheer Him up . . . so he got all of his juggler's paraphernalia out from under his bed, dressed in his costume, and did all of his best juggling and tricks for the Child.
Some of the monks heard the commotion and were about to interfere, when the juggler stopped, exhausted and out of breath (and out of practice). Just then, the Christ Child clapped and laughed, and the Blessed Mother came down from her niche and wiped the sweat from his brow.
Just a medieval legend - but a sweet one, I think!
Anatole France made a short story about it. There's also an opera by Massenet, and quite a number of paintings and books.