Interstate rest room joke

Traveling down the interstate and needing to use the restroom,
I stop at a rest area and head to the restroom.

I was barely sitting down when I heard a voice from the other stall saying:
"Hi, how are you?"

I'm not the type to start a conversation in the restroom and I don't know what got into me, but I answered, somewhat embarrassed,
"Doin' just fine!"

And the other person says:
"So what are you up to?"

What kind of question is that? At that point, I'm thinking this is too bizarre so I say:
"Uhhh, I'm like you, just traveling!"

At this point I am just trying to get out as fast as I can when I hear another question.
"Can I come over?"

OK, this question is just too weird for me but I figured I could just be polite and end the conversation. I tell them
"No. . . I'm a little busy right now!!!"

Then I hear the person say nervously...
"Listen, I'll have to call you back.
There's an idiot in the other stall who keeps answering all my questions”.