Gregory Tiernan (born June 19, 1965) is an Irish-born, Canadian-based animator, director and voice artist. Along with his wife Nicole Stinn, he founded Nitrogen Studios Canada, Inc. in 2003, through which he introduced CGI to the Thomas & Friends series. Prior to this, Tiernan collaborated on various projects with filmmaker Don Bluth, Walt Disney Animation Studios and Klasky Csupo, Inc.

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