Tom Bombadil's
pony who is "
larger, stronger, fatter (and older)" than
Merry Brandybuck's ponies. Ol' Fatty keeps the ponies out of trouble when the hobbits wander into the
barrow-downs. However, there's no Fatty to save them from the
Watcher of
Moria, and there
Samwise Gamgee loses his best buddy next to
Frodo,
Bill the pony.
Fatty appears in
The Fellowship of the Ring.