In a 2023 leak of unreleased content from different iOS games, an app titled Angry Birds Island - or alternatively Angry Birds Hatchery - was discovered. The prototype was simply a version of the original Angry Birds with two major differences
•A mode called "Hatchery", which shows an overworld map of an island with a row at the bottom of toys and furniture
•The first two worlds of the original game, but with an option to select from a set of birds, all of which appear to be hybrids of the regular birds
This seemingly implies some kind of pet simulator mode with an egg breeding mechanic, not unlike the Chao Gardens from the Sonic Adventure series. It is unknown if this was planned as an update for Angry Birds or a new spin-off.