Mark Feuerstein's Been Behind The Two-Way Mirror While People Judge Him

The 9JKL star swapped notes with Stephen Colbert on experiencing the "testing" process for his new series.

The new CBS comedy 9JKL is based on an awkwardly intimate situation from Mark Feuerstein's life, when he lived as an adult in an apartment owned by his parents—and was sandwiched between their unit and his brother's. The series premieres on Monday, Oct. 2 at 8:30/7:30c on CBS and CBS All Access.

Also an awkwardly intimate situation from Mark's life? Sitting behind a two-way mirror while people judged and criticized him.

The process is known as "testing" in the entertainment industry, and is used to get honest opinions about a new show. Since Mark happens to be an Executive Producer as well as the star of 9JKL, he went to watch—and it may have felt a bit personal!

He shared what it was like during a visit to The Late Show, and Stephen was able to commiserate.

WATCH: Mark Feuerstein Answers: Is 9JKL Based On Real Events?



The two also spoke about the influence of the legendary comedian Steve Martin, who was also a guest on Thursday's show.

READ: Get Closer To 9JKL Star Mark Feuerstein... But Not That Close

Watch all-new episodes of The Late Show with Stephen Colbert weeknights at 11:35/10:35c on CBS and CBS All Access.

Watch the series premiere of 9JKL on Monday, Oct. 2 at 8:30/7:30c on CBS and CBS All Access.