"Drop by" means an "unplanned visit", so not more than to say hello. Kind of like:
[Doorbell rings, the portier opens the door and takes John to the studio.]
- Hello, Mark.
- Hello, John.
- Guy.
- John.
[Long silence.]
- So, eh ..., till next time, then?
- Till next time, John.
- You two take care now.
- Bye, John.
[John leaves the building, gets inside the silver Range Rover, and pauses.]
- That should have been me ... THAT SHOULD HAVE BEEN MEEEEEE! YOU HEAR! DAMN YOU, GLEN!