The cast of Signature’s [title of show]. The characters in [title of show], the uber-meta musical now playing at Signature Theatre, pronounce in song that they’d rather be nine people’s favorite thing than 100 people’s ninth favorite thing. It’s an admirable admission, and while DCist’s assessment of them falls somewhere closer to the middle, musical theater geeks enamored by quick wit and a constant stream of clever allusions could easily be charmed into the…