Baby Ganesha in murti form is found rarely in Hindu Temples. A child form of Ganesha is worshipped at the famous Thirumandhamkunnu Temple at Angadipuram in Kerala. This form is worshipped below the peepal tree on the west side of the Bhadrakali Temple here.
King Mandhata had ruled the region for a very long period. Finally, he abdicated the throne and took Sannyasa. He then meditated on Shiva and attained the holiest Shivling in Kailash.
King Mandhata carried the Shivling to his kingdom and got it installed on a hill where the present Thirumandhamkunnu Temple is located.
This Shivling actually belonged to Goddess Parvati. When she realized it was missing, she asked Goddess Bhadrakali and Bhoothas to get it back from the king.
But it was not easy to take away what was gifted by Shiva. Finally, Bhadrakali took her most ferocious form and started pulling the Shivling to which the king was embracing.
Goddess Parvati then appeared at the temple with baby Ganesha and stopped the battle.
As Goddess Parvati appeared with child Ganesha, he is worshiped here in the form.
Read more about Thirumandhamkunnu Temple in Kerala