The original Angry Birds was planned to be launched on the DSi and Wii as a downloadable title on DSiWare and WiiWare shops, but was cancelled likely due to the release of 3DS in 2011 with its glasses free 3D. The Wii version would eventually be released, but as a part of Angry Birds Trilogy compilation.
The Trick or Treat episode was originally going to debut in the original Angry Birds instead of being in its own game, taking Ham Em' High's spot of being the 5th episode. It was also going to have 30 levels instead of 45. It was changed possibly because themed episodes would clutter up Classic, and having only one wouldn't be fitting. It was later renamed from Angry Birds Halloween to Angry Birds Seasons to focus on other holiday themed episodes.
A unreleased Angry Birds game known as either “Angry Birds Hatchery” or “Angry Birds Island” that featured a Hatchery mode, which is seemingly a customizable Island, alongside unique birds.
A chapter based on Jabba's Palace was planned, but was ultimately scrapped. The events of this chapter were instead covered by the first cutscene to Moon of Endor.
Artwork for pig versions of the Imperial Royal Guards exists, suggesting that they were planned to appear in the first Star Wars. They were never used there, but did end up appearing in Star Wars II as playable characters.
The Big Bang kart was originally going to be called the Exploder.
The Green Baron kart was originally going to be called the Crimson Baron.
Chuck's ability activation looked visually different compared to the actual depiction in the actual release. He appeared to transform himself (and his kart) into a high-speed rocket instead of slowing down time of his surroundings.
Concept art posted around 2020 to 2021 depicting Gale as the main character of a game similar to Angry Birds Match, unofficially named Angry Birds Gale Match. It's unknown if what exactly this game was going to be, but the most common consensus is that this was the original idea for Match.
Over the years, Rovio Entertainment soft-launched various Angry Birds games, many of which were created by other studios, and didn't last long.
Angry Birds Football, formerly known as Angry Birds Goal!, involved the team of "Mighty Feathers" (composed of Red and four unnamed red birds) and pigs facing off against each other in football matches.
Angry Birds Ace Fighter, a Shoot 'Em Up game with birds using fighter jets to shoot down pigs and rescue creatures that would give them passive effects.
Angry Birds Holiday, a buisiness management sim. In an attempt to distract pigs from stealing the eggs, the birds would have run a vacation resort services for them.
Angry Birds Islands was another building sim, combined with battling mechanics. Birds and pigs would team up with each other to fight against monsters to rescue piglets and collect and create resources.
Angry Birds Dice was a board game, similar to Monopoly in concept. The game had birds invited to Leonard's Cashio for a dice game.
Angry Birds Tennis was another spin-off, this time it was a game of Tennis. The game had two unsuccessfull soft-launches in 2020, before being completely shut down in September.
Angry Birds Legends was an RPG game, similar to Angry Birds Epic prior to it. The game was also launched alongside another Rovio title, Chronicles of Legends, which played identically to Angry Birds Legends, but didn't have any Angry Birds elements in it. This was done to see how usage of the Angry Birds impacted the game's performance. Both versions would eventually be shut down.
The series also had a lot of proposed, but ultimately cancelled games:
Angry Birds Hatchery Island was basically the same as version 2.0.0 of Angry Birds, but this game has a "hatchery" mode where you mix and match your own birds on an island, each with their own ability. This iOS game was found in the TestFlight Teraleak of December 2023.
Angry Birds Breaker was also found in the Teraleak. Only the icon resurfaces to this day, as the game is unplayable.
Angry Birds Space Assault!, an unreleased spinoff to Angry Birds Space by KLab America, described as a "3D action strategy collectable game". The project was first made public in May of 2019 when the designer Glen Dahlgren uploaded the contents to his portfolio.
A blooper reel for Angry Birds Toons showcasing several goofs and errors related to the character rigs has two clips of a cancelled winter-themed episode.
4th Street, the fourth season, was planned to be released sometime around 2017, but eventually delayed to 2018. It did however recieve an Early-Bird Release in December 2017 on iTunes and DVD.
The "Dream House" episode was originally going to be called "Coin", but changed around the main gag of the house due to the fact that piggies don't use money.
According to thesescreenshots, the series was to be originally animated in CGI instead of 2D animation.
Also, Stella is not pictured with Red, Chuck and Bomb in the above screenshots, meaning she possibly wasn't intended to be part of the main cast in the beginning.
This screenshot of an early logo for the series shows that it was originally going to be called Angry Birds: Summer Camp Madness.
An animated series titled Angry Birds Samuraiwas pitchedback in 2015. All that's known so far is that the series would have took place in feudal Japan with the birds and pigs being redesigned (similar to that of The Angry Birds Movie) to fit the country's premise.
Swear words (such as "damn, hell, crap", and even one instance of "ass") were intended to be in the film, but toned down in order to keep the PG rating.
Tobuscus was set to cameo in the film as a character named Perry, but his cameo was cut from the film due to accusations being put against him at around the same time.
The original plot draft and storyboards were more serious in tone involving the eagles after a golden egg hidden away by Mighty Eagle and were actively seeking it by attacking the pigs and then the birds islands themselves and Zeta's original name was Zelda.
The eagles were also far much larger and fiercer looking than the birds, pigs, and even Mighty Eagle
At one point in development alongside Terence, Matilda, Stella, and Ross were going to have a larger role in tagging along for the journey to Eagle Island.
Other:
A scrapped comic series Gale's Chronicles, developed roughly before January 2016, telling the story of Angry Birds Stella from Gale's perspective. It would have been about her developing as a character as time passes and learning to become a good queen.