Pete likes Jane and Anne. His friend Jack (all the four in their early teens), too, likes both the girls who, in their turns, like both the boys. To get sure which of the two possible pairs should date on on a permanent basis, Jack and Pete, and Jane and Anne as well, agreed to try changing their dates once in a while. A mutual friend of theirs, Tom, guessing the situation rather than knowing about the agreement, after the boys told him that they just went to watch the same movie in different places, wants to ask who went there with whom.
The variants of the question that I was able to think of are as they follow:
With whom who went to the movies this time?
Who with whom went to the movies this time?
Who of the two with did you go to the movies this time?
Who of the two did you go to the movies with this time?
My question is about the most casual question that Tom might ask to get the information he wants to get, like, "I (me), with Anne. Jack, with Jane." Are there any English expressions to describe the experiment carried out by the teens in the context? What can be said in short in colloquial English about their maybe strange yet somewhat rational way of dating?