After completing the entire game, and defeating the owl. When you have all the keys. In the cave you can find on the map a secret passage, going there, you will see a secret boss steel beaver, after defeating them you can get a secret trophy, in the form of a figurine of the beaver, even after the fight you will have a dialog with him

Here's a figurine of the beaver itself

And to get this pearl, you need to catch it 5 times on a fishing boat. And then it will help you to heal characters, it cannot be turned off

After getting all the characters, in game. You will get a small fan, it will help you by shooting at enemies, it also can not be turned off

After getting a Fredbear for your team, you can walk up to the main Fredbear, and get an ending like this

If you complete the game on the hard difficulty level, after defeating the owl, you can enter the tent, and fight Scott Cawthon, after defeating them you will also get a trophy in the main menu

During dialogs with Fredber, wait a little time, until he does not become pixelated, do so with each, in 4 locations, you can enter the portal, there after the conversation you will get a trophy in the form of a crying baby

If you pass correctly, pixel maze, you can get to the bay of the fisherman, approaching him, he will tell you that he is an Old Man Consequences, you can enter the lake, drowning there, you will get a trophy, in the form of a pixel bear