Out of interest, did you reach a conclusion? As far as I can tell, he uses them pretty interchangeably, leaning towards Rodney when they're together and McKay when referring to him with other people. But that's just a feeling...
I did! It evolves.
For season one, on the surface it seemed interchangeable at first until I looked at the dialogue a little closer. (Literally, I have pages.) The first time he called him "Rodney" was when introducing him to the kids in "Childhood's End", but he was being somewhat informal there, I think partly because they were kids. The first time he actually referred to him as Rodney in a conversation was the one quoted from "Underground". Up until "Sanctuary", he only uses Rodney when he's spectacularly frustrated/exasperated with him.
"Sanctuary", well, he's rather annoyed with McKay almost from the get go, so there's a lot of Rodney's in there, right up to the confrontation outside of Chaya's room where he gets pissed, and then he reverts back to McKay for the remainder of the episode.
This trend changes around "The Gift", sort of a turning point, because he's transitioned to using "Rodney" more casually. It's definitely more relaxed, and not during his exasperation at this point. When talking to other people though, it depends on who he's talking to and when. With Ford he refers to him as McKay almost all the time, with Teyla he transitions to referring to him as Rodney near the end of the season. (On a side note, it is also around "The Gift" that Teyla has started to refer to Ford as Aiden, but none of her other teammates yet). I believe with Elizabeth it's "McKay" during the first season.
...and that's just season one! (Aren't you sorry you asked?)
no subject
I did! It evolves.
For season one, on the surface it seemed interchangeable at first until I looked at the dialogue a little closer. (Literally, I have pages.) The first time he called him "Rodney" was when introducing him to the kids in "Childhood's End", but he was being somewhat informal there, I think partly because they were kids. The first time he actually referred to him as Rodney in a conversation was the one quoted from "Underground". Up until "Sanctuary", he only uses Rodney when he's spectacularly frustrated/exasperated with him.
"Sanctuary", well, he's rather annoyed with McKay almost from the get go, so there's a lot of Rodney's in there, right up to the confrontation outside of Chaya's room where he gets pissed, and then he reverts back to McKay for the remainder of the episode.
This trend changes around "The Gift", sort of a turning point, because he's transitioned to using "Rodney" more casually. It's definitely more relaxed, and not during his exasperation at this point. When talking to other people though, it depends on who he's talking to and when. With Ford he refers to him as McKay almost all the time, with Teyla he transitions to referring to him as Rodney near the end of the season. (On a side note, it is also around "The Gift" that Teyla has started to refer to Ford as Aiden, but none of her other teammates yet). I believe with Elizabeth it's "McKay" during the first season.
...and that's just season one! (Aren't you sorry you asked?)