Clark, a young bear wearing a Cubs jersey and backward blue baseball cap, was accompanied Monday at Advocate Illinois Masonic Medical Center by a dozen team prospects.
The mascot is named after the North Side Chicago street on which Wrigley Field is located.
Team officials say they held focus groups before deciding on Clark, and fans told them they wanted a more family-friendly atmosphere at Wrigley Field.
Clark will greet fans at Wrigley before and during games, and the mascot will have a Twitter account and Facebook page.
The Cubs had a live bear mascot in 1916, nine years after formally adopting the Cubs moniker.
Online: http://www.cubs.com/clark and http://twitter.com/ClarktheCub