Mystic pop up bar.
I love me a good fantasy but I haven’t yet come across one that I’d like to rewatch multiple times (or even at all) This one checks the boxes though.

Splish Splash Love (actually listed on Viki as Splash Splash Love) is a classic, short, feel-good time-travel drama about an unsuccessful student who goes back in time and learns about life, history and love, first-hand. It's a high-school drama and one needn't ask too much of it.

I'll totally second Mystic Pop-up Bar here too. There are some bumps on the way to the feel-good, but for me, that's the best kind of feel-good, an earned one.

From Now On, Showtime! Never have I ever come across such a fun bunch of ghosts who do magic shows!! 👻

Alchemy of Souls and Alchemy of Souls Season 2: Light and Shadow. An amazing amount of detail and world building. I love almost all characters and hate the villain with passion. Win-win.

The King: Eternal Monarch, again fantastical amount of world building and time slips. If nothing else just watch for the feel-good fantasy that is Lee Min-ho. 😊❤

The Legend of the Blue Sea, just because I want to squeeze in another Lee Min-ho drama and there is nothing more feel-good than him. 😉

The Tale of the Nine-Tailed and Tale of the Nine-Tailed, 1938. Lee Dong-wook, Kim Bum in suits. Nuff said. 😂

See You In My 19th Life, if you don't fall headlong in love with Seo-ha. Check for your heartbeat. Shin Hye-sun's performance is more fiery than her red hair.

Last but certainly not the least Extraordinary You!! 🤩💕 Everything and everyone is beyond adorable. A true blue feel-good fantasy.

Honorable Mentions:

Goblin, it has Gong Yoo and Lee Dong-wook, what is not to love.

Zombie Detective, Choi Jin-hyuk definitely feels good in this one. 😂💪🏻🧟‍♂️

The Atypical Family definitely surprising.

Totally agree about Splish Splash Love - an absolute must-see!

I think for me Twinkling Watermelon also fits nicely into this category. There are some heavier sections, but also lots of bromantic pettiness (in a mostly good way) and nostalgic high school feels.

You could also try Strong Woman Do Bong-soon? There is an annoyingly creepy/dark villain in the picture, but the leads are uncompromisingly feel-good and adorable. If you ever decide you're sick of the gangster storyline, you can skip right over those parts and lose nothing relevant.

Feel-good fantasies are one of my favorite genres:

_ Definitely you have to give a try to Twinkling Watermelon. One of the best fantasy shows.
_ The Best Hit. Somehow it's like the father of Twinkling Watermelon.
_ Hwayugi. Flawed but funny and entertaining.
_ Splash Splash Love and Vivid Romance. Short, light and definitely feel-good.
_ Dog knows everything. In a word: endearing.
_ Meow: Secret boy. Cute and nice. A comfort watch.
_ My Holo Love. With one of the sweetests MLs.

Deserving of the Name

Ghost Doctor

Unlock My Boss

May I Help You (Skipping the last case)

Familiar Wife

W

Faith

Arang and the Magistrate

365 Days: Repeat the Year (It's fantasy crime thriller, but not overly dark, depends on how much that makes you feel good!)

Room No. 9 (same as above)

I agree with Mystic Pop-up Bar (I really enjoyed that one!) and Twinkling Watermelon (with a little warning that one has to first plough through the first episodes to get to the feel-good stuff).
And if Go Back Couple counts, a big yes as well. 💕

Adding
- Hello, Me
- Queen Cheorin (aka Mr. Queen)
- Crash Landing On You (because sadly, that was still a fantasy)

(And if I may sneak in a cdrama, The Romance of Tiger and Rose 🙂)

Not a kdrama, but LOST ROMANCE would be my feel-good fantasy drama recommendation. Good comedy, fun romance, spunky and savvy FL, and a really swoony Marcus Cheng as the ML (or both MLs, depending on how you look at it).

Mr. Queen, except you need to fan fic the ending; the chef stays with his King and they live happily for many years. The soul of the queen comes up from the pool, and there's a whole new season about her. She learns to live as a handsome, strong man in our time - after some beginner's difficulties she can't believe that life can be that easy. She can't cook, but she's a master embroiderer, and even if some few people in this time are as good as her , they are just women, and as a man she gets much more attention and everybody are in awe of her and she gets TV-shows and what not.

A good day to be a dog ... ending with episode 8.
My Love from the Star - except for the murders and betrayals
Mystic Pop Up Bar
Strong Girl/Woman Bong-soo - except for the kidnapper. I have not problem with the gangster scenes , even if they are vulgar.
With reservations again for the violence and well, bad things;
See you in my 19th Life, and
Doom at your Service.
My Demon? No, probably not, there's too much evil and sadness ... but there are some very happy moments along the way.
Zombie Detective
Atypical Family - at least in the end. It's pretty sombre from the beginning.
I am not sure about Extraordinary You - would those of you who've seen it say it ends happily enough to be feel-good?

For a similar body switching theme in a movie format and the Christmas movie "Switch" (2023) is right up your alley. It has some of the best movie dialogue and ending I've seen in Korean movies (or any movies). Light but with depth, witty, funny, thought-provoking, tinged with just a bit of bittersweet. You're going to love it.
Feel good fantasy dramas with depth: Come Back Mister, Missing: The Other Side I & II, Tunnel, Marry My Husband, Rooftop Prince, Master's Sun, Yume Wo Kanaeru Zo, Hello Francesca. Of these, I would recommend Come Back Mister first because it's a relatively lesser known K-drama gem in the fantasy genre. It aired at the same time as the Song-Song drama but was the much better watch (at least for me)