Mr. Pilkington is the owner of Foxwood, one of the neighbors to Animal Farm. The narrator tells us that he is “an easy-going gentleman farmer who spent most of his time in fishing or hunting according to the season” (4.2). He is on bad terms with the other neighbor, Mr. Frederick; “These two disliked each other so much that it was difficult for them to come to any agreement, even in defence of their own interests” (4.2). The antagonism makes much more sense when you realize that Mr. Pilkington is a symbol for the West – both the United States and the United Kingdom – and the neighbor he quarrels with is a stand in for Germany.
Both Pilkington and Frederick are worried about the Rebellion on Animal Farm because they think the revolutionary spirit might spread to their own animals. We learn that Pilkington speaks of “terrible wickedness” that takes place on Animal Farm in order to maintain peace on his own (4.3). Once Napoleon re-opens business relations with humans, he sometimes deals with Pilkington and sometimes with Frederick, but never with both simultaneously.
Things become complicated between Pilkington and Napoleon when Napoleon goes back on his promise to sell Pilkington a pile of timber. For a while, Napoleon’s relations with Pilkington are “almost friendly,” and Napoleon seems to hate Frederick as much as Pilkington does (8.7). At the last minute, however, Napoleon switches and sells the timber to Frederick. The next thing you know, the animals on the farm are chanting “Death to Pilkington” (8.11).
However, when Napoleon realizes that Frederick has cheated him, he sends some pigeons to Pilkington hoping to patch up their relations. As Frederick and his men advance on Animal Farm, the pigeons return with a simple message: “Serves you right” (8.16). The relations between Animal Farm and Foxwood appear to be severed.
The entire episode is an allusion to the infamous non-aggression pact that Stalin signed with Hitler in 1939. Hitler and Stalin had been enemies for years; throughout the 1930s, communist parties around the world defined their mission almost entirely in terms of anti-fascism. Earlier, Stalin had nearly signed on to an anti-German alliance with Britain and France, before negotiations broke down and the alliance fell apart. Therefore the 1939 announcement of a non-aggression pact between Nazi Germany and Stalin's Russia came as a shock, deeply disillusioning left-leaning idealists (people like George Orwell) who had still been holding onto belief in the supposed socialist ideals of the Soviet Union. The non-aggression pact seemed to prove that Stalin was just another tyrant, that all the Soviet rhetoric about workers' revolution had become mere propaganda. Only when Hitler broke the pact by launching a massive surprise invasion of Russia in June 1941 did Stalin suddenly return to his earlier anti-fascist pose, seeking alliance with the West in opposition to Hitler. (See "Symbols, Imagery, Allegory" for more on the non-aggression pact.)
At the end of the novel, Pilkington has been invited over to Napoleon’s farmhouse for a fancy dinner. The scene probably represents the Tehran Conference, a meeting held in 1943 between the leaders of the United Kingdom, the United States, and the Soviet Union. At the meeting, Stalin, British Prime Minister Winston Churchill, and American President Franklin D. Roosevelt came to agreement on joint military strategy for the rest of the war and began to make plans for the postwar order. Among those plans was a virtual Soviet takeover of much of Eastern Europe. (See "Symbols, Imagery, Allegory" for more details on the Tehran Conference.)
Since Animal Farm ends with a depiction of this conference, the mood is both upbeat and uneasy. Pilkington makes a toast to Napoleon, and jokes, “If you have your lower animals to contend with, we have our lower classes!” (10.24). The book ends with Pilkington and Napoleon scowling at each other when they “both played an ace simultaneously.” In other words, they discover that they have both been cheating at a game of cards (10.31). Orwell, before most, saw that this alliance between Russia and the West was artificial, full of tension, and bound for failure.