Hearing the curse, the wives of both the brothers got worried and they beseeched the saint to excuse their husband s. the saint replied, "They will be rid of this curse when Shri Krishna will appear in Gokul". Since the curse was uttered these trees had been standing in front of Nand Baba's house. So, to keep up the word given by Saint Narda to the wives of the two brothers, Krishna dragged the mortar crawling in between the trees. The mortar got stuck up between them and when Krishna exerted force, the trees got uprooted and fell down. As soon as the trees fell down, they changed into their real forms as sons of Kubera. With folded hands, they began to praise Krishna and after seeking his permission, they returned to their place.
Note: Damodar means "One who has rope around his belly'. Dam - Rope, Udar - Stomach/Belly
Also read about:
1. Sri Sri Damodarashtakam - Prayer to Krishna in month of Kartik (in Sanskrit, English, Its meaning and Video)
http://krishnaseva.blogspot.com/2014/05/sri-sri-damodarashtakam-in-sanskrit.html
2. Krishna Leela - His mercy on poor fruit seller:
http://krishnaseva.blogspot.in/2014/08/lord-krishnas-mercy-on-poor-fruit-seller.html