Actor Robert Michael Morris has passed away. He was 77.

The comedian best known for his role on Lisa Kudrow's The Comeback passed away on Tuesday to still unknown causes, according to Deadline.

Morris started out as a theater teacher in New York City before finding his breakout role in the off-Broadway play Cary Churchill Cloud Nine directed by Tommy Tune. His former student Michael Patrick King offered him the role of Valerie Cherish's (Kudrow) hairdresser and "guard dog" Mickey in The Comeback in 2005. He reprised the fan-favorite role when HBO revived the comedy in 2014.

His other credits included Will & Grace, Arrested Development, How I Met Your Mother and 2 Broke Girls.He most recently appeared on ABC's The Middle as Stan Hoister.

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"Robert Michael Morris was an inspiration to write for and to be around," King said of his former mentor. "His creativity was only matched by the joy and gratefulness he felt for each day he got to live his life as an artist."