Tom Cavanagh – Conner, the firm's brilliant but irresponsible ad copywriter who began his partnership less than a decade ago with Mason. Twitchy Conner is a bachelor with a checkered history of failed romances and a growing debt to the company which he incurred by abusing the expense account.
Eric McCormack – Mason McGuire, the firm's newly promoted Creative Director and straitlaced family man. Mason's levelheaded nature often counteracts Conner's unpredictable behavior even though Mason is highly neurotic. He works well with Conner because of their work ethic but he has workaholic tendencies that affect his marriage.