Complex sentence: During his shift as Santa, Willie is visited by Thurman, an exceedingly naive, overweight boy, who believes Willie is actually Santa and is the target of taunts from a skateboarding gang.
Split into simpler sentences: During his shift as Santa, Willie is visited by Thurman, an exceedingly naive, overweight boy, who believes Willie is actually Santa. The boy is the target of taunts from a skateboarding gang.