You must play each minigame and unlock a hidden animatronic head before finishing the minigame. You will know this is complete when the minigame star glitches out.

Fishing: A glitched spot at the bottom right of the fishing border will randomly appear during any round. You must hook into this spot and complete the minigame.
Topping Juggle: You must spam left at the beginning and complete the minigame.
Longest Popgoes: You must head into the distorted upper left corner of the map when it randomly appears after collecting a Pizza (WITHOUT COLLECTING ANY MORE PIZZA), collect the head in the center, leave the hidden room and finish the minigame.
Pest Control: You must hold all three buttons at the start of the round, defeat the head that appears, and finish the minigame.
Whack A Rabbit: You must wait for the rabbits at the start of the round to enter their third stage. One of them will have a special animatronic head on when they reach the third stage. Attack all of the rabbits that do not wear the head when they enter the third stage, but spare the one who does. Finish the minigame when they disappear.

After completing all of these, your diary should begin glitching out. You must check the new Diary entry which appears at the end of all previous diary entries.