Smile is a character in the Funkin' Physics mod who is fought in his song of the same name. He was once an average human lumberjack named Frederick before being sent a cruel online joke at his expense that got him to try and hang himself in the woods, during which he met a strange, tall man and mysteriously transformed into a trollge.

Origins

Smile was once a normal human being named "Frederick", he had a job as a lumberjack, and loved to socialize online, due to his good and kind-hearted self, he was a "Snowflake", he was targeted by many trolls online that would push his buttons in a bad way. But there was one thing that got to him, when he was online, a troll asked if he wanted to know a hilarious joke, he agreed then the troll asked him to go to his bathroom and look in the mirror, he then realized that he WAS the joke, then the troll asked if that was "the funniest joke ever", he then answers the troll with "I sure am laughing, I’m smiling." Then the troll asks him to kill himself, then Frederick accepts it. Fred then goes out into the woods and finds a branch to hang himself on, then encounters a strange tall figure covered in black, then he was reported missing for weeks.

More facts here: https://fridaynightfunking.fandom.com/wiki/Funkin'_Physics?so=search#Bonus_Characters