Anything ever done by Monty Python whose comedic gold, acting, writing and the general enjoyment the creators had working on it can just make you laugh and enjoy their work WAAAY too much!
Cold Case may be about people who are already dead, but it still manages to be very positive and life-affirming, with characters learning and growing and reaching for their dreams. Rare is the episode that doesn't leave you with warm fuzzies.
Pushing Daisies. Brightly colored sets, fantastic clothing, impeccably witty dialogue, and amazing acting. Should rightly taste like diabetes, but somehow everything works out in its favor (even the combination of the sweetness of Ned and Chuck and gruesome murders).
Gilmore Girls. The love that the mother and daughter have for each other, and not only that, even with all the troubles, Stars Hollow and the Gilmores are good people inside their hearts.
Mork & Mindy. Both the show and the titular couple. So much sweetness and optimism... why is it they don't make shows like this anymore?
Too Cute. A show about cute puppies and kittens growing up. Pure, concentrated adorable.
The Golden Girls. Whenever I am depressed or upset, the Girls cheer me up. True comfort TV.
Full House, from reminding you of life lessons of all kinds each episode to delivering safe but nevertheless funny situations, Full House is definitely a contender of the picture of 90s sitcoms.
Any Star Trek episode with the word "Tribble" in the title. In the original "The Trouble with Tribbles," you can just feel that all the cast was having a merry time being comedians for a change in a genuinely funny and charming story.
Really, the idea behind Star Trek in general. There is hope for the future. Humanity will survive, will settle its differences, will solve all its own problems, and then...we will go forth into the universe and be awesome.
There's something so friendly and familiar about (most of) TNG in particular that makes it excellent Sweet Dreams Fuel.
It's more than that. It just perfectly encapsulates childhood, period, with a healthy dose of exaggeration. All the problems that seem petty looking back are displayed with outrageous importance, blown up to proportions that by all logic should seem too absurd to take seriously, but the characters are so genuine and their reactions so familiar and close to home that the lengths the conflicts are taken to seem justifiably as important now as they were then. The show takes you back to how it felt to search desperately for a missing Ear Worm or how unfair curfews seemed or how the local bully acted like a monster. But with that you get how it felt to have a crush, or end a fight with a friend, or do something nice for someone, or even just to relax. This show is an epic, feel-good tribute to what it means to be a kid and have fun without tasting like diabetes for a single moment. And it makes you laugh. So, yeah, perfect.
"You take the good, you take the bad, you take them both and then you have The Facts of Life!"
Family Ties is definitely sweet dreams fuel for anyone who was a child in the 1980s.
iCarly: iSaved Your Life. Freddie would sacrifice his life to save Carly, Carly realises how much he means to her, they kiss about 6 times in a very cute way (and one hot way in the extended version). They practically glow with happiness whilst they are together, and the final 'dawww', Freddie has a I Want My Beloved to Be Happy moment because he doesn't want to hurt Carly by taking advantage of her when he's unsure if her feelings are true. Even though it's a minor Downer Ending, it's a very powerful expression of his feelings for her and that it's not just some random teenage hormonal attraction on a show with practically no morals, aesops or lessons.
Also the relationships between Spencer and Carly, and Sam and Carly. Whilst most of the show isn't especially heartwarming, the 3 major relationships, Spencer/Carly, Carly/Sam and Freddie/Carly are a heartwarming core of warm fuzziness.
Big Time Rush: A lighthearted comedy about four pretty, childish boys going on zany adventures. Add an innocent song about love or good times in almost every episode, and it's impossible to watch without feeling all warm and fuzzy inside.
The Joy of Painting with Bob Ross. There is a reason all the trees are happy! Every episode showed that anyone can create a nice-looking landscape painting in no time at all using very simple techniques and few tools. Being guided by Ross, the perpetually pleasant, all-around nice guy, was just part of the fun. In fact, one German TV channel used to broadcast it around 3 AM, without dubbing, specifically for its soothing qualities. Literal Sweet Dreams Fuel for the insomniac.
Some days are special. Some days are so, so blessed. Some days, nobody dies at all. Now and then, every once in a very long while, every day in a million days, when the wind stands fair and the Doctor comes to call...everybody lives.
The Fish Fingers and Custard scene from "The Eleventh Hour". It's one of the funniest and cutest scenes in the episode. 
In fact, any scene that involves Eleven and a little kid will most likely result in this trope.
What about the 2011 Christmas special's ending, when the Doctor arrives at the Ponds?
What about Amy and Rory's wedding? Everything about that day is perfect, from her parents being brought back to reality, to Amy and Rory being happy and safe and able to be together, to the Doctor dancing like a loon to the three of them riding off in the TARDIS together.
Near the end of the finale for season six, the scene where River goes home to Amy and Rory's place, and Amy's whoops of joy when she finds out the Doctor's alive.
The entire show which has taught whole generations of people that a hero is a slightly barmy alien with a screwdriver who is a huge fan of our planet. Even his ship thinks we're bigger on the inside.
To save the universe, you don't need weapons. You don't need superpowers. You just need your mind, your friends, and hope.
Fraggle Rock. Not many shows are created with the intention of bringing about world peace.
In 2013-14, Beta Patrol released a few indie Cover Albums of the show, which have a few tracks that fit this trope. Radiation City's retraux-y "I'd Give My Soul", Transmissions' haunting "Let Me Be Your Song", and The Boys And Girls' sweet and folky "Friendship Song" are among the highlights.
Kamen Rider Fourzedoes have some moments when you might need additional SDF, it deserves a mention for the rest of the show, which is easily the most idealistic (and lighthearted) entry in the franchise - this is made even more heartwarming when you consider that the production team wanted a hero who could bring smiles to people's faces after the 2011 Earthquake. C'mon, Switch ON!
The Ultraman franchise is full of it (Although some series may fall into the complete opposite category). Every series has just tons of Awesome Music, a cast of likable characters, and loads of (for some, goofy) fun. There's also the recurring themes like determination, hope, following your dreams, and protecting what matters (Earth, friends and family, the future, and those who cannot protect themselves) in nearly every series that are extremely uplifting and much needed in a time when everyone seems so pessimistic about everything.
Entries that should be especially emphasized as SDF include:
The original Ultraman. It's such a classic and just so full of old-timey charm and fun!
Ultraman Max is a throwback to everything that made the original series so great, from its easy-to-root-for cast to its balance of heart and action. There's an overarching theme of believing in the best in people in a world where everyone thinks Humans Are Bastards (which reaches its culmination in the Grand Finale).
Ultraman X — A series where the protagonist's dream is to build a world where both humans and kaiju can live alongside peacefully. Naturally, it has plenty of great moments that will put a smile on your face.
Speaking of "golden age" Nickelodeon: Want your SNICK back? Now you can, with this extremely faithful recreation of theoriginallineup as it stood during the 1993 holiday season, complete with 1993 commercials! To add to the nostalgia, the mastermind behind the video recommended watching it every Saturday night at 7:57pm - try it out on the YouTube app on the Wii U, Xbox One, PS4, or LG Smart TV!
The Recycled: The Series version of Fame, despite its more dramatic moments, has some excellent original songs that beautifully complement the show, such as Life Is A Celebration, Starmaker, Beautiful Dreamer, Shadows and Light, Reach For A Dream, Other Side Of The Road, and many others.
How I Met Your Mother is an example of a show pulling off an all around nostalgic feel from the perspective of a guy looking back at the best years of his life leading up to him meeting the girl of his dreams. The main five all operate on the friendliness they share with each other, and there are quite a few episodes with endings underscored by upbeat rock songs.
A specific example in the final season would be Cristin Milioti's rendition of "La Vie En Rose," which Ted hears and falls in love with before even meeting Tracy McConnell herself!
Also Marshall and Lily as a couple have to be one of the most adorable pairs on television.
The ending of the season four finale has all five members of the group triumphantly jumping from the rooftop of Ted's building to the neighboring one, with "Prophets" by A.C. Newman playing as Ted declares the year the best of his life. Overlaps with Awesome Moments.
Parks and Recreation. A show about the values of hard work and passion, the wonders of love and friendship, and the importance of community, all wrapped in some very funny comedy. The finale is especially great, with everyone getting a perfectly-tailored happy ending.
Scrubs, with its endless optimism and quirky characters.
Its 2015 follow-up, simply titled The Muppets, also fits this trope, being a Work Com in the veins of Community and Parks and Rec.
The Japanese Spider-Man show. Everything about it is so lovably goofy (and awesome) that it's hard not to get a smile on your face when you hear the opening theme. Even Stan Lee himself is a fan of the series.
Anything related to The Hollywood Squares- it's a show with humor running rampant and not much of a "game", and it also has amazingly catchy theme tunes as well.
Ditto Match Game- lots of freewheeling fun with not much at stake, funky music and bright colors.
You can chalk that to any Game Show where seeing contestants get to win lots of money and prizes can uplift the spirits of just about anyone.
You wouldn't think The Twilight Zone would be just as apt to run on this as Nightmare Fuel, but you get episodes like "Night of the Meek" (a depressed Mall Santa gets a bag full of wishes and ends up becoming Santa in his own right), "One for the Angels" (a small-time peddler is able to make an epic sales pitch to Death himself, and saves a little girl in the process), and "I Sing the Body Electric" (aka "The Electric Grandmother")
Unbreakable Kimmy Schmidt: The show is about a girl who has been kidnapped and trapped for 15 years, but, as the title says, is such a strong Determinator that nothing can break her. The show is realist on the sense that hard work demands sacrifice, not everything will be 100% great all the time and that you might fail a lot, but greatly values one's attempts to become a better person and it's determination of never giving up. By season 3, it's immensely noticeable the amount of how the characters evolved in people who, although still flawed, are fighters.
Kimmy: I'm not gonna give up, and neither are you! Titus: I'm trying to protect you! Kimmy: Protect me from what?The worst thing that ever happened to me happened in my own frontyard. Life beats you up, Titus, doesn't matter if you've been kidnapped by a cult or if you've been rejected over and over in an audition. Titus: Some of which you paid to attend. Kimmy: You can either curl up in a ball and die like we made Cynee do that time, or you can stand up and say: "We're different! We are the strong ones! And you can't break us!"
John and Sherlock at the end of "A Study In Pink".
Sherlock saving Irene Adler at the end of "A Scandal In Belgravia".
Almost everything from "The Sign of Three", from Sherlock's best man speech, to Sherlock convincing Sholto to allow John to save his life, to Sherlock's Odd Friendship with Archie, and Sherlock revealing that Mary's pregnant, and that she and John will be great parents.
Sherlock and Eurus at the end of "The Final Problem". Also, Mary's closing narration.
From the first episode:
Lestrade: Sherlock Holmes is a great man. And if we're very lucky, one day, he might even be a good one. From the final episode:
Police Officer: He's a great man, sir.
Lestrade:No, he's better than that. he's a good one.
British series In the Night Garden... was deliberately intended to be this. The point of the show was to provide children with something calming to watch at night, a time when they should be winding down for bedtime.