Agent Sean was, with Agent Luxury, one of the first Bad Slash agents named, first appearing in the fourth mission in the Original Series, "Protector of the Ringbearer." His main activities in the PPC appear to have been keeping the nymphomaniacal Lux occupied. Yes, occupied. Before the end of the Original Series they had apparently broken up, and were no longer partnered. After this, he does not seem to appear again.
Sean has, or had, blue hair and multiple piercings, and was a notorious tinker. His current situation is unknown.