Not only was Bob Martin one of the co-writers (along with Don McKellar) on the libretto for The Drowsy Chaperone, he also starred as Man in Chair in the original Broadway production. In 2006, he was nominated for a Tony Award for his performance, and he won the Tony Award for Best Book of a Musical. However, the musical originated when some of Martin's friends, including lyricist Lisa Lambert, performed a short play in the style of Marx Brothers revues and 20's-era musical theatre as a gift to Martin and his fiancé (now wife), who is incidentally named Janet van de Graaff. After this performance, Martin decided to join Lambert in developing the show further, adding on McKellar and musician Greg Morrison to the team.
The role of Man in Chair actually wasn't in the initial versions of the musical. As the show developed, he was added as a framing device for the rest of the piece. To quote McKellar, "We knew the general public would be baffled if they saw this show without someone sort of saying, 'You're allowed to laugh.'" And so, Man in Chair came to be. Martin was the only member of the aforementioned team who hadn't been performing in the show, so he ended up fitting in very nicely to the kind of outsider that Man in Chair personifies. He also brought in his own improv experience for developing the character, and little quirks of his own (for instance, a hobby for collecting things and the kind of anxiety we hear Man in Chair talk about at the start of the show). Specifically, regarding the moment in which he says that he's feeling "a little self-conscious anxiety, resulting in nonspecific sadness," Martin's own wife said it was "very Bob."
Ultimately, of the original team, Martin was the only one who retained his performative role in the show because the rest were replaced by Broadway-caliber triple threats who also needed to dance and sing. The producers and Martin's co-creators considered him too integral to be replaced, and there was a written agreement as the show was being optioned that he had to open the show on Broadway.