Krakowski's character was Ally McBeal's assistant, I'm not sure what the plotline was, but I imagine she was pursuing some sort of theater dream.
The role of Cassie was written for one of the most brilliant and hard-working dancers Broadway has seen. Krakowski--self-admittedly--has good dancing skills but she is by no means a trained dancer in the way that Donna McKechnie is a trained dancer. Krakowski might be able to learn the choreography and perform it for a special occasion but I doubt she could perform it eight times a week, especially when she rarely practices her dancing skills.
She is fantastic in that clip and her vocals are great, I wish she had performed the whole song and with the original Bennett choreography like everyone else said. I would love to see her back on Broadway.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"