Skeletal Rooster

The Skeletal Rooster is seen crowing before the musical number, "Jack's Obsession".

It's the only time it is seen in the entire movie.

As he seems to be entirely “functional” (being usually lethargic, and then rising and crowing to indicate dawn), and he resembles the Skeletal Reindeer in concept, it is possible that the Skeletal Rooster was created at some point in the past by Dr. Finkelstein, possibly at Jack's request.

Before the sunrise