<human>:  Why was the silent film star Roscoe Arbuckle called the “Fatty Arbuckle”?
<bot>: Roscoe Arbuckle was a very fat man, and was called Fatty by his fellow actors in the 1920’s. He was a very popular actor and comedic actor in the silent film era. He was known for his physical comedy, and was often the center of attention on stage.