The Best Friend Mechanic (BFM) is a system that decides who should appear in Chapter 5 to cheer Lucy up before she goes back to the forest. Every children of Silentown has a chance to be in the spot, depending on how the player plays. In order to have a specific character show up, you have to max them by fulfilling the events below. The choices are mutually exclusive, so you can't max out more than one character at a time, if no character is maxed, the cat (Squinty) will appear.
Blue:
Suggest doing the "trick shot" to Blue. (Chapter 1)
Reply to Silver that you do believe Blue's stories in Barn Alley. (Chapter 2)
Make a "Not so scary" horror story. (Chapter 2)
Find Blue in his secret hideout. (Chapter 4)
Red:
Do not play the Spy. (Chapter 2)
Make a "Very scary" horror story. (Chapter 2)
Say that Brains are better than Brawns in the argument between Red and Black. (Chapter 4)
Lie to Raven saying that Black was already captured. (Chapter 4)
Black
Do not play the Spy. (Chapter 2)
Make a "Very scary" horror story. (Chapter 2)
Say that Brawns are better than Brains in the argument between Red and Black. (Chapter 4)
Silver
Don't take Blue's side while interacting in Barn Alley. (Chapter 2)
Do not play the spy. (Chapter 2)
Make a "Not so scary" horror story. (Chapter 2)
Do not hit him. (Chapter 3)
Sunny
Suggest doing a normal pass to Blue. (Chapter 1)
Play the Spy. (Chapter 2)
Tell her what is going on behind the Barn. (Chapter 2)
Make a "Not so scary" horror story. (Chapter 2)
Bring the scissors back to her. (Chapter 3)
Say that you will protect her when she is scared. (Chapter 4)
Raven:
Suggest doing a normal pass to Blue. (Chapter 1)
Do not play the spy. (Chapter 2)
Make a "Very scary" horror story. (Chapter 2)
Admit you also hear the voices from the forest. (Chapter 3)
Do not lie to her (bring Black back before her). (Chapter 4)
Say that Brains are better than Brawns in the argument between Red and Black. (Chapter 4)