Arthur is a friendly feline who is always biting Suzaku. He was first found by Euphie and Suzaku when he was injured, and taken care of by Euphie. Later Arthur got a hold of Zero's mask and it became a cat hunt. The one who caught the cat got a kiss from any member of the student council. Suzaku and Lelouch were the ones that got the cat and got a kiss on the check from Nunnally. Arthur was quickly adopted into the student council meeting room as his new home. When Suzaku was 'killed'
Arthur would sit at his grave sort of like he was guarding it. In the Avalon he was sitting in front of Lelouch and acted like he knows what was being said and agreeing on what Lelouch said.