Nigel was the agent for the group The Be Sharps. He supposedly has a tattoo under his hair.
He discovered the group while they were performing at Moe's Tavern, where he became their agent. He consistently tried to trick his clients and take advantage of their success.
Nigel once became the agent of Santa's Little Helper after he became famous. Once again he attempted to make a profit off of his client's success, even going so far as to thwart Bart's efforts to win his dog back.