It’s amazing to hear that people celebrate animal wedding to fulfill their own wishes. Wishes may be personal or related with unique group of people. In case of group all people involved in ceremony and do all arrangement required to complete celebration.
In India monsoon is decisions maker for agricultural crops. More than 80 percent of farmer depends on monsoon for irrigation. Weak monsoon cause insufficient rain that cause farmer crops to fail.
To overcome this trouble they perform old tradition like wedding of frog, donkey to satisfy god associated with problem. It is believed in India that Indra is god of rain and he initializes all activity related with rain.
People select random animal from their habitat and act with them like real people and perform every ritual which they do with real person. They assumed after completing this act god will please and do rain.
In rare case real person marry with specific animal to secure luck. When person take birth then it is believed that before birth god written his destiny. One can get rid of bad luck by wedding with animal. In India some tribes girl marry with dog so that her bad luck passed on to the dog .After that she can marry with person of her choice .
These ceremonies are widely accepted in their respective communities. They try to perform ritual precisely and spend same amount of money that cost to real person event. They respect animal and after performing rituals they leave them at their respective habitat. In other cases animal raise as a pet after wedding celebration.