Question: Who plays charlie on it's always sunny?

context: No context provided
question: Who does Charlie Day play on It's Always Sunny in Philadelphia?
short_answers: Charlie Kelly
context: Charles Rutherford Kelly is a fictional character on the FX series "It's Always Sunny in Philadelphia", portrayed by Charlie Day. Charlie is co-owner at Paddy's (although he later sells his shares) and a childhood friend of Mac and Dennis. He is also Frank's roommate and possible biological child (""Dennis and Dee Get a New Dad""). He is addicted to various harmful substances (such as glue and alcohol), and is called illiterate by their peers (""The Gang Gives Back""). 
question: Who plays Charlie Kelly on It's Always Sunny in Philadelphia?
short_answers: Charlie Day

Answer: Charlie Day plays the fictional character Charlie Kelly in the FX series It's Always Sunny in Philadelphia. Day is an American actor, screenwriter, producer, and comedian who is best known for playing Charlie Kelly on the sitcom, for which he was nominated for a Critics' Choice Television Award and a Satellite Award in 2011.