“Who Doesn’t Love Musicals?” is the title of tonight’s episode – which means, I’m pleased to report, we’ll get more of Megan Mullally as Franny, who’s writing a Broadway musical about Fiona (Lisa Kudrow) and has agreed to accept some of Fiona’s input. With Whose Line Is It Anyway also on TV, this show makes Tuesdays an especially good night for fans of improvisational comedy.