Some (mostly independent) wrestlers still go to great lengths to ensure that their real names are not publicly known. It is a highly respected tradition in Mexican lucha libre for performers to hide their true identities, usually wrestling under masks, and revealing a luchador's identity without their permission is considered a serious offence with real-life consequences. Professional wrestlers are often referred to by their contemporaries by their ring name. In interviews, Bret Hart regularly referred to Mark Calaway, Curt Hennig, and Kevin Nash by their ring names (The Undertaker, Mr. Perfect, and Diesel). Ring names are often trademarked by the promotion that creates a character or gimmick for a performer. It is common to see one performer use a variety of ring names throughout their career, even if their overall persona remains similar. This is especially true in WWE, which has largely forced most wrestlers that have debuted since 2006 to use a WWE-owned ring name instead of a ring name that they used on the independent circuit or, such as with Daniel Bryan and a few others, their real name. One notable exception was made for David Otunga because of his real marriage to singer Jennifer Hudson at the time, which gave WWE some mainstream exposure.