Sam was a super-earnest goody-two-shoes teenager from 1997. She went to Coal Hill School, but as a boring straight cis white girl who was neither a jock nor a nerd and didn't have dead or disabled parents, she didn't get to fight shadow monster things or anything. When the Eighth Doctor saved her from mean pushers who wouldn't let her just say no to drugs, she started following him around. But he dropped her off at a Greenpeace rally, which she couldn't resist.
Stalk Much? Edit
The Doctor spent two or three years adventuring with Ice Warriors and Cherley Pollard and anyone else who could make him forget how annoying Sam was, then grudgingly picked her up after the Greenpeace rally. He immediately tried to ditch her for a San Francisco doctor lady who totally wasn't that one from the TV movie that nobody was sure about the rights to, but Sam followed him into the TARDIS and not-Grace didn't. Then he left her on another planet to do some Space Greenpeace volunteering, but a couple years later she returned. Then he managed to lose her halfway across the galaxy, but, separated from his TARDIS, he could only flee in space, not time, and she managed to meet him again. He even got her killed, but some timey-wimey happened, and… The Sam came back, the very next day. The Sam came back, we thought she was a goner. But the Sam came back, she just couldn't stay away.
Love, American Style Edit
Sam didn't just want to be a companion. At first, she fancied the Doctor because, well, he looks like Paul McGann, so duh. But soon, she fell deeply, madly, whinily, mopily in love with him, and spent pages monologuing about how he'd never notice her love. (Obviously, Russell T. Davies never read any of the relevant books, especially the one where they made the Smith & Jones joke.)
Dork Sam Edit
The one interesting thing about Sam was that it turned out that she was such an annoying perfect companion for the Doctor because some sinister force had changed history to create a perfect companion for the Doctor as some kind of trap, for some reason that was never adequately explained. (Obviously, Stephen Moffat never read any of the relevant books.) This deep mystery was implied across multiple books, until being resolved all at once in one story.
The Doctor and friends ran into the original version of Sam, who was like totally dark and stuff—she smoked cigarettes, and had tried drugs, and wasn't even a vegetarian. Dark Sam tried to shag the Doctor instead of just mooning over him like Whitebread Sam, but got rejected because he doesn't do that kind of thing (another thing Stephen Moffat never read). Then she tried to shag Fitz, and he's not space Gandalf, he's just a horny guy from the 60s, so they shagged lots of times, because the books are more grown-up than TV. And then she walked into a crack in time and got erased from history (something else Stephen Moffat never read), only this crack was caused by the an evil bad guy twisting up the Doctor's timeline which she had to walk into to save all of history (a different thing Stephen Moffat never read). The readers were left wondering, "Seriously? That was the fabled Dark Sam we waited 23 books for? That's it?"
Fortunately, SJ was much more capable than the Eighth Doctor: it wasn't long before Sam died, and then died a different way, and then got totally erased from history, so SJ could get some less annoying companions like Rani Chandra.
Behind the Scenes Edit
Sam was hastily created when the BBC couldn't figure out whether or not they had the rights to use Grace, from the TV movie. The second EDA, Vampire Science, was rewritten to replace Grace with a totally different San Francisco lady doctor that the Eighth Doctor somehow knew, and write in the throwaway character from the end of The Eight Doctors as a permanent companion instead of the lady doctor.
The cleverest thing about her is that she was a girl, but had a name that most people think of as a boy's name. Like Jo, Mel, Ace, Benny, Evelyn, Charley, asBill, and Mickey Smith.
The OrmanBlum were not very happy with their creation. The fans were even less happy. And the other writers even less so. Nobody liked Sam. But editor Stephen Cole wouldn't let anyone kill her off, no matter how much they begged. Finally, Mad Larry managed to sneak her exit into a 69105-page book that was too complicated for Cole to understand. Once Sam was out of the TARDIS for good, her editorial protection field was broken, and soon she was retroactively killed two different ways.
In the Big Finish audios, even though they by this point took place in an entirely independent alternate timeline from the novels, Gary Russell went out of his way to erase Sam from history.
But, thanks to Gary's permanent continuity boner, he was unable to resist putting a reference to her into Torchwood: Martha Jones uses the name Samantha as an alias in one episode, which nobody would have suspected was a Sam Jones reference if he hadn't tweeted that Martha had heard the name from Sarah Jane and readers would know what he meant. Sigh. I'm sure she still hangs out with Sssssard in Gary-canon.
Why doesn't Gary Russell have a page here, anyway? If Chibnall and Levine had a baby and then raised it to hear no human language except Doctor Who, Gary Russell would still nitpick that kid's continuity references.