Every actor to have played the Doctor, with only a couple of exceptions, blend a handful of strikingly handsome or even beautiful physical traits with a slightly larger amount of funny-looking ones. Add in the requisite dorky mannerisms, charisma and loveable character acting and you've got the recipe for over 50 years of slightly embarrassing Celeb Crushes. Steven Moffat said every actor to play the Doctor should be "arresting" and "attractive in a very odd way".
The Rills in Galaxy 4 are another Beauty Equals Goodness subversion and look quite endearingly like walruses.
The Marshchild from Full Circle, a creature that's essentially a baby swamp monster. In one of the first scenes in which it appears, it's shown peering at the Doctor from behind a fallen tree, its obvious timidity combined with its endearingly ugly face giving it an almost irresistible cuteness. That cuteness is only enhanced by a subsequent scene in which it's shown materializing in a spaceship corridor behind the Doctor, only to go scurrying back out of sight a moment later. It doesn't help that its subsequent ill-treatment by a bunch of (apparent) humans propels it firmly into Woobie territory.
Daleks in general, at least their metal casings. What's not to love about a metal pepper shaker with a plunger and half an eggbeater for arms? Special reference goes to the squeaky-voiced and gurgly humanised Daleks in "The Evil of the Daleks", Dalek Caan and the Ironside in "Victory of the Daleks".
The Ood. Due to their benevolence and the fact they are all Woobies, once you get past the fact they've got mince meat where their mouths should be, they are very sweet.
The tiny old Doctor that the Master kept in a birdcage from the S3 finale. He was so tiny and sad! And kind of looked like Tweety Bird, between the birdcage and the huge head. Also, there's something very endearing about the Doctor's personality in that minuscule body.
The baby Adiposians. Basically a pound of roughly humanoid animated fat. Possibly the cutest thing the show has ever featured. They become less cute when you remember that that pound of humanoid animated fat killed people when they came into existence, although 99% just detach from a human and walk away one by one. The main characters even comment that it's not that bad a weight loss program, all things considered.
The Gangers are incomplete, unstable copies of human beings, all with a smooth, featureless Nightmare Face with visible veins that looks like they are melting. They also managed to look vulnerable and sweet, especially the positively dainty Ganger of Jennifer.
The youngest Slitheen in The Sarah Jane Adventures episode "Revenge of the Slitheen" - "Daddy, I want to hunt!"
Mr. Sweet from The Crimson Horror has elements of this, with his big black eyes.
The P'Ting from the Tsuranga Conundrum. Relentless, bad-tempered, highly dangerous, and something to be desperately avoided, it still manages to be adorable especially when it has a full belly.
The Mandalorian: Creator Jon Favreau notes that a lot of early designs for Grogu had "Disney proportions," while he deliberately wanted to "ugly up all the different individual features," adding the hair on his ears and the sharp fangs. On the other hand...look at him!
Rex (a Coelurosauravus, a reptile resembling an Indonesian Flying Lizard) and the Diictodon (small mammal-like reptiles best described as reptilian gophers mixed with pigs).
Nimrod, the baby mammal-like-reptile-sea-creature-thing from NBC's short-lived series Surface. Come on, who wouldn't want to love a creature that, when full grown, can swallow a small boat whole, burrow through miles of rock, sunbathe in a magma chamber, secrete a substance that lets it regenerate injuries, and generate bolts of lightning?
A lot of the Muppets not deliberately designed to be "traditionally cute" could count, actually; especially some of the Grouches (just don't tell them that).
Star Trek: The Next Generation had cute alien critters from time to time. A bug-like species in the episode "The Most Toys" and a thing that Worf's son Alexander becomes fond of in "New Ground".
Star Trek: Deep Space Nine has Nog. Like all Ferengi, he’s pretty much straight Ugly by human standards... until he tries to purchase an apprenticeship in Starfleet.
ALF was most likely designed with these intentions.
It would seem that one of the biggest reasons for the success of The Munsters was their ability to create quaint, relatable people based on classic Universal horror icons. Fred Gwynne as Herman Munster in particular is just plain adorable.
Young Oswald Cobblepot (the future Penguin) in Gotham. Pasty-pale complexion, Sinister Schnoz, hair that looks like a bird's nested in it, and scraggly yellow teeth... and yet almost Bishōnen in an odd way, with his wide green eyes and oddly winsome smile.
Pigmon, who first appeared in the original Ultraman, a red biped about the size of a child and with a gentle and friendly personality towards humans. In most of its appearances, it helps the human characters in some way, such as warning them team of a monster's arrival, befriending a child, or taking care of people trapped in Kaiju territory. Unfortunately, Pigmon is usually killed by the Monster of the Week while protecting humans.
Also from Ultraman is Gyango, a scaly humanoid creature with a mischievous personality manifested from a wishing stone. Initially human-sized, it's ordered by the thief that stole the stone to play pranks on people at a hotel, but ends up knocking out its master when he foolishly commanded it to grow giant while both of them were indoors. Even as a giant monster, Gyango still retains its humorous personality and engages in comical slapstick with Ultraman during their battle.
Eleking from the same series as Miclas is considered cute by Japanese fans, despite being a 55-meter tall mix of an eyeless electric eel, a giant salamander with antennae, and Godzilla. A Chibi version of the monster appears in Ultraman Mebius as the Team Pet.
A number of fans consider Zetton II from Return of Ultraman to be this, as while his suit is rather shoddy-looking compared to the sleek, menacing original Zetton from Ultraman, he has chubbier proportions and floppy horns that end up making him look like a fat rabbit. It should be noted however that while he may look unintentionally cute, his role as the final threat of the series is anything but.
A lot of the kaiju in Ultraman Cosmos could be considered this, as they're generally Gentle Giants. A good example is Mogrudon, a giant blue mole who often acts like a big puppy dog.
For some viewers, Lord Beelzebub, in a very scruffy Bifauxnen sort of way.
LazyTown: While the puppet characters fall into the Unintentional Uncanny Valley most of the time, their personalities are charming and likeable, making them seem adorable rather than creepy.
