At age three, Donna Lynne Champlin started tap lessons. At seven she was tickling the ivories. She mastered the flute at nine and was singing professionally by eleven.

“I was that kid,” chirps Champlin. “I liked talking with my teachers about Broadway.”

So it’s not surprising that her costarring role in the CW’s tuneful comedy Crazy Ex-Girlfriend, now in its second season, is nothing short of a dream.

The series — about Manhattan lawyer Rebecca Bunch (star, creator and executive producer Rachel Bloom), who stalks her secret crush, Josh (Vincent Rodriguez III), to West Covina, California — comes complete with fantastical, full-blown musical moments.

Champlin plays Paula, Rachel’s needy bestie who tries to help her eccentric friend land her man. Along the way, she gets to dance and belt out some of the show’s original songs, like the martyr’s anthem “After Everything I Have Done for You.”

“Paula is how I used to be before I got lots of therapy,” says Champlin, wry but serious. “She’s a very kind, giving person, but unfortunately she is insecure and has no boundaries.”

Born and raised in Rochester, New York, Champlin depended on the practical guidance she received from her mom, a technical writer, and dad, a chemist for Kodak. “They told me I needed to be dedicated.” She was.

After graduating from Pittsburgh’s Carnegie Mellon, the four-time national tap champion made her Broadway debut in James Joyce’s The Dead, followed by parts in By Jeeves, Sweeney Todd (in which she played the accordion, piano and flute) and Billy Elliot. In 2007, she won an Obie for her turn as mother Cora in William Inge’s The Dark at the Top of the Stairs.

Before Ex-Girlfriend, Champlin’s TV work included guest spots on Law & Order, Younger and The Good Wife. When she was called to read for Paula, she knew she’d found a kindred spirit in Bloom. “There’s no ego with her.” On the set, “it’s always about the story and how can we do this together.”

Nowadays Champlin’s not going Hollywood hip. A wild night involves playing board games with her husband, actor Andrew Arrow, and their five-year-old son, Charlie. “We teach him about atoms. We’re super-nerdy.”