Christina Applegate has quit "Up All Night," which means it's time once again to keep track of all the many, many, many changes that have been made since NBC debuted the sitcom a season and a half ago:

* In the original pilot episode, Applegate and Maya Rudolph's characters were PR specialists. By the time the series made it to air, Rudolph was a talk show host, and Applegate her producer.

* Midway through the first season, the talk show got new management, and Applegate had a new boss to deal with.

* At the start of the second season, the talk show was canceled, and all the characters who worked on it other than Applegate and Rudolph's were eliminated from the show.

* Where the original premise had involved Will Arnett's lawyer choosing to be a stay-at-home dad while Applegate worked, in the new season, Applegate became primary caregiver, and Arnett went back to work — not as a lawyer, but as a contractor, working alongside Applegate's previously-unseen brother.

* When none of that worked, NBC put production on hiatus and announced plans to retool it as a traditional multi-cam comedy shot in front of a live studio audience.

* While that retooling was underway, the show's creator Emily Spivey quit — no doubt in frustration over how little the show now resembled the one she had devised.

And now Applegate is leaving — in a statement, she said, “It’s been a great experience working  on Up All Night, but the show has taken a different creative direction and I decided it was best for me to move on to other endeavors. Working with Lorne Michaels has been a dream come true and I am grateful he brought me into his TV family.  I will miss the cast, producers and crew, and wish them the best always." — even though she, Rudolph and Arnett are the only reasons this ridiculous experiment is happening. NBC could have canceled the show and tried to start over with this same cast, but they'd have been releasing the actors from their contracts — which, given Applegate's exit, weren't that iron-clad to begin with.

NBC wouldn't comment on Applegate's departure, but Deadline's story on the departure suggests that NBC executives still won't give up the ghost, and are looking at other actresses like Lisa Kudrow to step in and play Reagan.

Give it up, guys. It's over. You can keep reshuffling the deck chairs, but the ship be sinking.