Remember how Seinfeld is often described as "the show about nothing", with episodes revolving around frozen yogurt, ponies or parking spaces? Well, Pie-o-My could be considered an almost Seinfeldian moment in the history of The Sopranos, since a large part of the story is centered around... a horse.
The animal in question, which gives the episode its title, is a race horse Ralph has bought on Hesh's suggestion to make some extra money. Tony is introduced to the creature one day and unexpectedly finds himself attached to Pie-o-My, whereas Ralphie coldly resorts to violence to make her run faster. On the home front, Carmela's worries for the future increase, leading her to ask Tony to sign a life insurance policy.
At first sight, one could classify this episode as irrelevant, and you couldn't blame anyone for doing so: nothing substantial happens, apart from Ralph and Tony's differences emerging clearer and clearer as the story progresses. With hindsight, though, Pie-o-My is as superb as other episodes because it sets the suspense for the second half of the season, which will see some characters hit new lows in their life.
Plus, a horse: reminds of the Godfather, doesn't it?