I've never recced this story, despite the fact that I've probably read it three or four times by now (I try and wait a year between rereads, so yeah, its been awhile). I'm not entirely sure why that might be. Maybe I just never got around to it. Or maybe it too closely walked the fine line between the cannon Sexual Tension that makes me love Sam/Jack in the series - all sorts of fun situations with shippy value without actually having any on-screen romantic sappy stuff - and actually *making* Sam/Jack an item, complete with all the sap, smut, and romance that usually involves in fan fic, that I tend to try and avoid. But, since I've read it numerous times now and still love it, I suppose that it just manages to say this side (or "my side", I suppose) of the line.
This Cannot Be Happening by Jojo. Sam is "accidentally" sent to another reality by... well, herself, I suppose, and as always tends to happen when SG-1 is involved in pretty much anything, she ends up getting dropped smack-dab in the middle of the mystery her double left behind. And its a doozie.
While the story is heavy on the Sam/Jack shippiness, it doesn't *seem* heavy on the Sam/Jack shippiness. What shippiness there is is limited - for most of the story, at least - to all those pesky "what if" thoughts and feelings that pop up in the series quite often, actually. And most of them are Sam's, since the story - while third person - it told from her perspective. Also, because she's stuck in an alternate reality with a Jack that kind of hates her (at first), said thoughts and feelings tend to center around "her" Jack, who is still back in her original reality, making the story relatively sap-free.
Right. No idea if that made any sense what so ever. Anyway, Personal Issues of Sam and Jacks aside, the story captures the fun and humor of Season 4 (the scene where some of the things that Sam drunkenly stated at New Years come out is a personal favorite of mine), and it has a solid, mystery-based plot that will hook you from the start and keep you reading until you finish several hours later (yes, even after you've read it three times). And, best of all, nothing really sappy until the Epilogue(s).
Also, there is a kind of sort of companion piece that really isn't a necessary read but which is fun none the less
Bed Hopping. And it isn't so much a "companion" piece as a "extremely vague reference to" in This Cannot Be Happening.