Despite his name, he is a loving and caring pony, he is just easily fooled by his daughter's shenanigans.
Filthy Rich is the grandson of Stinking Rich, who was one of the first customers to buy Zap Apple Jam from the Apple family and sell it in his store, which, over time, became Barnyard Bargains, the largest retail chain in Ponyville (sort-of like the Wal-Mart of Equestria).
Whenever someone calls him "Filthy," he corrects them, statng that he'd rather be called "Rich."
His wife is Spoiled Rich (nee Milk).
Family Appreciation Day
Where the Apple Lies