Normally, I love this show. Even when I'm not familiar with the comedian, of not a fan, there's something enjoyable about the banter between Jerry and his guests. I like the stories of how it was starting out, and some of the funny stuff that happens along the way.
This was reminiscent of the episode with "Kramer," from the old Seinfeld show. That didn't work too well, but it had it's moments. Sadly, this one does not. I smiled/lightly chuckled five times in twenty minutes. I counted. The character of "Miranda Sings" (or whatever) just doesn't work.
The only time the show really came alive was at the very end, when the actress underneath actually started talking about how the character affected her life. Could have flipped the show. Had one minute of Miranda, and nineteen of Colleen.
A rare, but serious misstep of an episode, in an otherwise fascinating show.