Bill was purchased in Bree after all the horses and ponies in The Prancing Pony's stable had been set free or stolen, including the ponies that had been brought by Merry, Frodo, Pippin, and Sam. Bill Ferny sold them Bill for twelve silver pennies, which was three times his real value. Bill was described as being old, weak, and sickly. Barliman Butterbur, the innkeeper of the Prancing Pony, paid for Bill and gave Merry an additional eighteen pence to make up for the disappearance of the other ponies.
During Bill's stay with the Fellowship in Rivendell, it was observed that his once poor health had improved and Rivendell had a similar renewing effect on all the members of the Fellowship.
When the creature of the lake (Watcher in the Water, which killed Óin brother of Glóin) attacked, Bill fled in fear. Sam, who cared for him greatly and had grown attached to him, thought him to be dead, and grieved. He also feared that Bill had been devoured by wolves. However, Gandalf had previously spoken to Bill, "words of guard and guiding," reminding him of what he had learned in Rivendell and advising him to go where there was grass and at last return to Elrond's place or wherever he wished to go. On their way home, the Company found he had returned safely to Bree. Bill played a small part in the winning of the Battle of Bywater by kicking his former master, Bill Ferny, in the backside, and thereby freeing the Shire from further entanglements from the foul man.
Portrayal in adaptations
In The Lord of the Rings (1978 film) The Watchers tentacles go near him, and Sam says "Poor old Bill. Poor old Bill.", indicating the pony has been killed.
The Lord of the Rings film trilogy
In Peter Jackson's The Lord of the Rings: The Fellowship of the Ring, however, Bill is released before the Fellowship enters Moria since they cannot take him into the Mines. Sam gives his beloved pony a fond farewell while Aragorn assures him that Bill knows the way home, and he walks away into the night.
In LEGO The Lord of the Rings, Bill the Pony is mentioned in the "Pass of Caradhras" level. In this level he can be found in a concealed cave as a secret Easter Egg. Also, the player will receive the treasure item Bill's riding crop upon finding him.
his theme song https://www.youtube.com/watch?v=C79AOi9vKeE