A fat, but good-natured pony, Fatty Lumpkin lived in and around the Old Forest with his owner Tom Bombadil. Although small, Fatty Lumpkin was able to carry a grown man with out any trouble.

When Merry's ponies fled the Barrow-wights, they found Fatty Lumpkin and stayed with him until Bombadil called for them.
Encyclopedia entry originally written by shirehobbit