Almost all well-formed English sentences have a verb. Most grammar books for ELLs suggest that we can understand imperative sentences as having the implied "You" as the subject. For example,
Sit down. (= You sit down.)
I noticed that in a movie I watched, it has this sentence, Judah Buckner to the rescue, which can be generalized to the construction: X to the rescue.
Though the meaning is clear, I would like to know how to analyze this construction as a sentence. Should I regard it as a fragment? Or should I understand it as an ellipsis, as shown below?
Superman to the rescue.
(= Here is Superman to the rescue.?)
(= Here comes Superman to the rescue.?)