There are many secrets in Grand Theft Auto games. All articles about secrets will be linked to this page with Category:Secrets. These secrets are put in the game deliberately by the developers Rockstar Games.
For example, the Andromada is a very large plane used in one mission on Grand Theft Auto: San Andreas, but is not obtainable by any other means. However, you can Spawn the plane using a Trainer, and fly it as a normal plane.
Another example is at the top of the Gant Bridge, where a sign says "There are no Easter Eggs up here, Go away".
See the main article: Easter Eggs