Day 12: Character you don’t like seeing paired with anyone else
When you get right down to it, most of my OTPs I prefer not to see with anyone else, and usually at least one party of the ship I won’t enjoy them with anyone else in canon and certainly not read them with anyone else in fic. There may be a caveat to the effect of ‘If party A didn’t exist I might have shipped party B with party C, but party A does exist so...no,’ but if it’s in any way canon it must treat A/B correctly before I can get to B/C.
However, it there’s a greater example for me of this than the Doctor I’m not sure what it is. For me Rose is the one true love of the Doctor’s existence. To ship Rose with anyone else I have to invent an entire headcanon crossover AU and pair her with another character I absolutely love and it’s STILL easier for me to ship her with someone else than it is for me to see the Doctor with anyone but Rose. I have a certain respect for Doctor/Master but mostly as a history rather than something that would work now and that’s the closest I get with him; anything Doctor/Jack is really the OT3 where Rose just isn’t there, and anything from Moffat’s era just doesn’t appeal to me nor do I believe it would actually deal with the Rose history properly to make me believe he’d love someone else. Anything else possible in the long history of the character I don’t really care.
The Doctor, in the TARDIS, with Rose Tyler, that’s the way it’s supposed to be.
Day 1: Your first ship ever Day 2: A ship you've just discovered Day 3: Your OTP Day 4: Favorite crack pairing Day 5: A crossover pairing you think would work Day 6: Series that you have many ships in Day 7: A pairing that disappointed you Day 8: A pairing only you seem to like Day 9: Your least favorite couple Day 10: Ship that became canon even though you didn’t expect it to Day 11: Character you like with several othersDay 12: Character you don’t like seeing paired with anyone else
Day 13: Couple you ship that causes intense feelings in its fandom (read: flamewars and the like)
Day 14: Couple you liked even though you knew it would end up badly
Day 15: A ship canon really messed with
Day 16: Favorite villain pairing
Day 17: Ship you talk(ed) about with people in real life
Day 18: Most annoying character that tried to come between a ship
Day 19: Favorite Hero/Villain pairing
Day 20: Favorite couple played for laughs
Day 21: Favorite opposites attract couple
Day 22: Saddest unrequited love
Day 23: Couple you only shipped after a long time
Day 24: Couple you like, but is overshadowed by another couple in a fandom
Day 25: Most popular couple in your favorite fandom (do you ship it too?)
Day 26: Best historical couple
Day 27: Another couple you shipped a long time ago
Day 28: A couple you shipped not nearly as long as you thought you would
Day 29: Favorite ‘birds of a feather flock together’ couple
Day 30: Couple you will still ship a few years from now