You will get a screen with a pink note and Freddy's theme playing in the background reading; At the end of a custom level (Easy or not) you will see the bonus ending of the game.
NOTICE OF TERMINATION
REASON: Tampering with the animatronics. General unprofessionalism. Odor.
After this, the player will be returned to the title screen. If the player had input the code 20/20/20/20 and got the notice, there will be a third star added onto the menu.
A rumor is constantly said that special numbers such as "1 9 8 7", "0 6 6 6", "1 3 3 7", 2-0-1-5 and more will let you receive a special ending. None of these codes work, with the exception of 1/9/8/7, and possibly 2-0-1-5 which, if you have the latest update, will cause the Yellow Freddy death screen and crash the game with 2-0-1-5 being a rumor which has not been confirmed or denied.
Another rumor was that if you put in the code 0/6/6/6, the Kitchen camera would activate. This is proven false, as no files exist in-game for the Kitchen's camera. also you will find a lot more jumpscares in the 20/20/20/20 you need to watch mostly foxy because he is the most active one.
SPOILERS END HERE!