To give the kid all the cakes:
On night 1 or 2, go to cam 8 and double-click BB.
Grab the seven balloons because why not.
Jump up and to the left, into the wall. You'll go through it and fall. Go right and grab the balloon.
Then on night 2, go to cam 7 and click the left yellow buttons on the arcade machine in the following order: top-left, bottom-left, top-right, bottom-right.
Go all the way to the right, then jump into the top part of the wall. You'll go through it and fall. Go left, up the balloons, and grab the cake.
Then, still on night 2, go to cam 8 and double-click BB.
Jump up and to the left, into the wall, fall, and land on a balloon. Jump on the balloons and give the kid some cake.
Then on night 3, click the cupcakes on cams 2, 3, 4, and 6. Go right one screen and down one screen, then jump over the left wall and jump on the balloons. Give the kid some cake.
Then on night 4, there's a 3x3 grid in the tiles on the wall. The top-left tile is the one behind the red guitar, and the bottom-right tile is just barely touching the trash can. You can click tiles and they'll darken, so do that to confirm the positions.
Click the top-right tile, then the bottom-right, then the very center, then the top-center, then the left-center, then the bottom-center, in that order.
Go to the right, then run left into the wall. You'll slide through to the left side and fall. When you land, go to the right until you enter a screen with an exit door. Stay on the left side of the screen and jump into the left wall. You'll fly up and land on the roof. Go to the left and jump. You'll hit the right wall in the next screen and fly up onto the roof again.
Go left and jump around until you float into the room above. Then head right. You'll float onto the roof. Jump into the room above, then head left. You'll float onto the roof of that building. Then head right. You'll pass through the wall. GIve the kid some cake.
Then on night 5, double-click the dark Bonnie figure on the right side of your desk. Hold down the S key and head left. You'll go through the wall and fall onto the kid. Cake.
Then, still on night 5, go to cam 3 and double-click the Puppet on the right. Head right and give the kid some cake.
Boom. Third star. Extras unlocked.