Question about tenses used in Seinfeld show: "what you were doing tomorrow night"

In the sentences

"Did she even ask you what you were doing tomorrow night? If you were busy?"

occurring at about 0:42 - 0:43 in this clip, why was past tense used in "What you were doing tomorrow night", when he was speaking about the future?

Solution 1:

"Did she even ask you what you were doing tomorrow night? If you were busy?"

Your example is about indirect reported speech that is using the backshift preterite (that is, a past-tense verb) for the subordinate clauses that are expressing what had been asked by her. She had asked something like:

• "What are you doing tomorrow night? Are you busy?"

Because that kind of info is being reported indirectly by subordinate clauses, their present-tense verbs can, or could, be replaced by backshift preterites. And that is exactly what happened in your original example.

Here are some posts with some more info on the main uses of the preterite, which includes the backshift:

• https://english.stackexchange.com/a/144712/57102

• https://english.stackexchange.com/a/172420/57102

Solution 2:

I believe it's in that tense because he is referring what the plans were at that time, not the actual future events that will be occurring tomorrow night.

If your plans change you don't say "We are going to the game next week but it's too expensive so we are watching at home instead."

you say "We were going to the game next week but it's too expensive so we are watching at home instead."