grammar - Use of object pronouns after the verb "to be" and in the presence of a conjunction.

The other day my friend and I were playing darts with several other players. We selected teams. When I learned that my partner would be Jordan, I enthusiastically announced,

"Hey Jordan, it's you and me!"

My friend objected that I should have said "Hey Jordan, it's you and I," for the same reason that one announces at the door of a friend who wonders who is outside, "It is I."

I find "It is I" rather pompous, but it seems correct. "Hey Jordan, it's you and I," on the other hand, seems incorrect. What is the rule here?