Bird-Pig alliance

The Bird-Pig Alliance is an alliance formed after the unexpected end of the Great Egg War, a conflict between the Birds and the Pigs, in response to the imminent threat of Zeta's plot to destroy both Bird Island and Piggy Island so that she would have a larger resort all to herself. The Birds and Pigs came to develop friendships and put aside former grudges during their joint effort to defeat Zeta and was warmed by her reunion and final marriage with her lover Mighty Eagle, allowing such alliance to endure further.

History
The Great Egg War ended abruptly when its last battle, the Battle of Overseas Pranks, was interrupted by the appearance of a larger threat that was ultimately directed towards both Birds and Pigs - a powerful superweapon manned by Zeta and her eagles from Eagle Island. After the first shot was fired towards his kingdom, Leonard, ruler of the Pigs, called for an emergency truce for the war against the Birds in hopes of trying to make sense of who or what just attacked them.

After knowing the truth of the attack's origins, Leonard traveled to Bird Island personally with his elite SQUEAL Team Six to meet with Red at his house to explain his emergency truce and the need to forge an alliance between Birds and Pigs to save their homelands. After Leonard successfully convinces Red, the two went throughout the island assembling a strike team to destroy Zeta's superweapon, rounding up Chuck, Bomb and Silver as the best Birds for the mission. They all then meet at Mighty Eagle's cave along with Mighty Eagle himself and Courtney to discuss a plan, only to be interrupted when Zeta destroys the cave.

Leonard then brings the team aboard his submarine to introduce them to other Pigs and their new inventions, before they all travel to Eagle Island to begin their mission. A great struggle against Zeta and her eagles ensued once they came to the island, ending with the total destruction of her weapon. With the mission a success, the team returned to Bird Island, where Birds and Pigs alike gathered on the beach to witness Mighty Eagle finally marrying a redeemed Zeta and rediscovering his lost daughter Debbie, whom Zeta raised alone without him up to that point.

Throughout the Birds and Pigs' mission to defeat Zeta, the Birds and Pigs were able to put aside past grudges and develop amicable relations to accomplish their goals, and the outcome of their efforts affirmed the alliance's viability in the future. To commemorate these friendly ties, Leonard commissioned drones to sculpt out the faces of the strike team onto the remains of Mighty Eagle's cave.

Some time later, an unseen force begins to infest the known world with bubbles, spawning strange one-eyed creatures and trapping hatchlings and piglets alike in bubbles. The Bird-Pig alliance once again had no problem with stepping up to work together and battle this new threat.