It's pretty common these days (though the trope is older than you might think) for kids to be portrayed as particularly creepy, in some way. This happens especially in horror movies, but may happen in various genres, and the kids may be dead (ghosts, zombies, etc.) or they may be possessed, or have supernatural powers, and in some cases may just be creepy without necessarily being dangerous or scary. Most often, it seems to be little girls rather than boys, and in fact my original intention in starting this page was to list creepy little girls. Maybe that's what I will do, though little boys can certainly be creepy, too. (I'll include a few boys on my list, and maybe I'll add more in the future.) If you check TV Tropes' Creepy Child page, you can see lots of girls and boys listed. (There's crossover with other TV Tropes pages, like Undead Child and Stringy-Haired Ghost Girl, and probably others.) Before I start my own list, I'll provide a few links to other sites with similar lists. (Okay, more than a few; I'm surprised at how many I found.) But some of these lists may include kids I'd consider too old to fit the trope. With few exceptions, I won't be including teenagers on my list.
The 5 Creepiest Kids in Movies... Ever!
10 Best Creepy Kid Movies of All Time
The 10 Creepiest Kids in Horror Movies
10 Creepy Horror Movie Kids
10 Creepy Movie Kids Even Angelina Jolie Wouldn't Adopt
10 Horror Flicks Filled with Creepy Kids
The 11 Best Creepy Little Horror Movie Girls
13 Scary Kids from Horror Movies
The 16 Creepiest Kids in Horror Movie History
20 Creepy Movie Kids to Put You Off Parenting
Carrie and 7 Other Creepy Girls You Wouldn't Dare Tease
Child's Prey: 15 Creepy Kids In Movies (Entertainment Weekly)
Creepiest Kids in Movie History
Creepiest Movie Children (Rotten Tomatoes)
Creepy Kids of Horror: Then and Now
Creepy Kids in Horror Movies
Creepy Kids of the Screen
Creepy Little Girl Movies
Creepy Little White Girls
Finn's Wake: My Top 5 Favorite Killer/Creepy Kid Movies
Pop Culture's Creepy Kids: Where Are They Now?
The Top 10 Creepiest Little Girls in Horror Films
Top 10 Creepy Girls in Fiction
The Top 10 Creepy Kid Movies
Top 10 Scariest Children in Horror Movies
Top 11 Creepy Kids
Top 11 Creepy Little Girls
Top 12 Creepiest Kids in Movies
Top Ten Creepy Kids
Top Ten Horror Movies Featuring Freaky Children
The Uncanny Factor: Why Little Girls Scare the S**t Out of Us
Why Are There So Many... Damned Kids (scanned from Entertainment Weekly)
Why Hollywood makes Creepy Kid movies, and why America can't look away
The Addams Family (1991)
This movie and its 1993 sequel included one of my favorite creepy girls, Wednesday Addams. She's not a ghost, she hasn't got powers, but she's definitely creepy and pretty cool. (I guess her brother, Pugsley, also sort of qualifies as a creepy kid, but he's not on the same level as Wednesday.)
This is an anime movie, which I know I had on VHS and watched once in the late 80s or early 90s, and then never saw again. I don't think I have the tape anymore, but I swear one day I'll get it on DVD or Blu-ray. Anyway, in the years since I saw it, whenever I try to think of creepy little girls from movies, this comes to mind... even though I don't specifically remember any of the characters or much about the plot. I kind of feel like it could have been when I first saw this that it first occurred to me that there was such a trope, but at the same time, I can't really think of anything I might have seen before this that fit the trope, so that seems unlikely.
Christa's one of those kids who aren't creepy per se, but have creepy powers. And it doesn't help that she doesn't yet understand or control her powers. So she's basically a sweet and lovely child who gets freaked out by the stuff that starts happening to her. And she is pretty dangerous.
The Bad Seed (1956)
I don't recall if I'd even heard of this before I started looking for the sites linked above, but a lot of them mention it as the prototype of the trope, so I should definitely see it sometime.
Bo is a sweet and lovely young girl with some seriously formidable powers, which she can't completely control.
Children of the Corn (1984)
I've never seen this, but I probably should.
Codename: Kids Next Door (2002-2008)
In this animated series, the Delightful Children from Down the Lane might qualify.
A horror short film involving a kidnapped girl.
In the Halloween episode (which aired in May on Hulu), there was a ghost girl named Amber who looked a lot like the ghost from "The Ring."
Deadtime Stories (2003)
A pilot for an MTV series that didn't get made, about a creepy girl named Ebola.
Elfen Lied (2004)
An anime series which is represented on a few of the sites above, but which I wouldn't have thought of mentioning. I guess Mariko counts, though the sites may mention a few other characters who are too old for me to include on my list.
The Exorcist (1973)
Regan MacNeil was a really sweet and cute, normal kid, until she got possessed. Then she turned into possibly the creepiest kid ever.
Ethan is an android child who definitely qualifies as creepy.
Weird Girl would qualify, as would some of the boys in this animated film.
Generator Rex (2010-2013)
In this animated series, Breach would pretty much qualify, though I'm not actually sure how old she is... she might be a bit too old for this list. But I'm not gonna let that bother me.
Get Off My Porch (2010)
A horror-comedy short film that involves a couple of young girls from a Girl Scout-like organization called "Adventure Girls." They're cute kids, and seemingly sweet, but... they may not be quite what they seem.
In season 3, a baby named Diana is born, and she definitely has some troubling powers. But she soon gets sent away, and we don't see her again until near the end of season 4, at which point she looks somewhat older than she actually is. Then we see her again in the latter part of season 5, having aged several more years since we last saw her. (I'd guess she looks about 8.) Anyway, Diana is now definitely creepy enough to be on this list... at least when she's not getting what she wants.
The Grudge (2004)
Toshio Saeki is a creepy ghost boy. Not as creepy as his ghost mom, but still.
Interview with the Vampire (1994)
Claudia is a vampire, so it's both natural that she's creepy, and kind of ironic that she looks more alive than many of the creepy kids on this list.
An anime series, in which one of the characters, Kanna, would seem to qualify. Though she's not really evil or anything, she's fairly creepy.
The Legend of Korra (2012-2014)
Eska and her brother Desna are a pair of very stoic, kind of creepy twins introduced in Book 2 of this animated series. They're a bit old for this list; I think they're in their late teens. But I still think they're worthy of mentioning.
Let Me In (2010)
This is based on a book, which I actually read before seeing the movie. There's a vampire girl named Abby (in the book, the character was called Eli). Um... I only watched this a few years ago, and already I don't remember it very clearly, but I suppose the girl must have been creepy. It's a remake of a 2008 Swedish movie, "Let the Right One In," which I'd really like to see someday, and would probably be creepier than this.
Meet the Robinsons (2007)
Lizzy has a very minor role in this movie, but I liked her a lot, because she reminded me of Wednesday Addams.
Miss Peregrine's Home for Peculiar Children (2011)
I haven't read this book and don't really know for sure that the kids in it are creepy, but I'm sure the vintage photographs are creepy... so for the moment, I've decided to use the girl on the book's cover as an image on this page.
I haven't seen this, and I'm not sure I want to. And I don't think it technically counts toward the trope, anyway... but still. It's on a lot of the lists above, so... whatever.
Pet Sematary (1989)
Gage, man. This is totally a spoiler I didn't reveal in my review of the movie (even though it's pretty much telegraphed from the beginning of the movie), but Gage... the toddler... eventually dies, and then comes back as an incredibly creepy little thing. (Incidentally, I didn't see this movie until 2016, shortly after I started watching Bravest Warriors, and when Gage came back to life, his voice reminded me a lot of Catbug.)
The Ring (2002)
This is a remake of a 1998 Japanese film (which I should try to see sometime). I watched the remake in 2014, and this is the movie that made me finally decide to start this page, which is probably something I'd vaguely thought of over the years. (Or maybe I hadn't really thought of starting such a page, but if not I should have, because I've thought of the trope often enough, and having my very own list to point to seems like a handy thing.) The girl in the movie, Samara, is a very creepy ghost (in the original she was named Sadako), and in fact the character helped spark renewed interest in the trope, apparently.
Scary Girl with Chloe Moretz (2011)
A four minute spoof of the trope on Funny or Die.
The Secret Saturdays (2008-2010)
In this animated series, there's a character named Francis who was probably in at least a couple episodes, and he's creepy enough to be worth mentioning.
The Shining (1980)
I think I've been aware of this movie for as long as I can remember, but I didn't actually see it until I was in college, sometime in the mid-90s. Anyway, I must have been aware of the creepy girls (the Grady twins) before I saw the movie. And they are certainly icons of the trope, who have been spoofed countless times in countless other things. But they're a relatively minor part of the film. Danny Torrance, one of the main characters, is also pretty creepy.
Sleep Tight (2016)
This is a horror anthology webseries consisting of several short films. One of the films, "The House," has a creepy little girl named Lily. Another film, "Exorsitter," has a demon-possessed little girl named Abby.
Something Wicked This Way Comes (1983)
A carny named Mr. Cooger turns into a creepy kid called "Robert," who pretends to be the nephew of one of the carnival's victims. There isn't really much I can say about that, but he may have played a more significant role in the novel than in the movie. Or not. I dunno.
Piper is a young girl who rarely speaks (to living people), ever since her parents died. But since then, she has found that she can speak to ghosts. And she definitely has a creepy look about her. But she's basically a sweet and cute kid who's just kind of shell-shocked. And she has a good relationship with her older brother, Connor (who started a paranormal investigation team mainly to help her come out of her shell).
I'm sure there've been a number of creepy kids on different episodes of this series, but I don't specifically remember most of them. Probably Lilith was the creepiest, though. And several seasons later, Amara.
The Twilight Zone (1959-1964)
I'm sure this anthology series must have had a number of creepy kids over the years, but I mainly remember Anthony Fremont, from the 1961 episode "It's a Good Life." He's a pretty iconic creepy kid.
Village of the Damned (1960)
Never saw it, but I should.
What It's Like Being Alone (2006)
An animated series in which any of the characters might qualify as creepy kids.
The Whispers (2015)
None of the kids on this show are inherently creepy; they're basically cute and innocent. However, an invisible alien entity pretends to be their friend in order to manipulate them into helping him achieve his goals (and he even ends up possessing one of them). So while under his influence, they become kind of creepy.
I'm sure there have been creepy kids in plenty of commercials (often as a "Shining" spoof, but not necessarily). So I started making a playlist.
...And I'm sure there are other characters I've seen whom I'm forgetting (especially if they only appeared in one episode of a TV series), as well as a bunch of movies and things I haven't seen and would like to, even if I haven't bothered to list them all here.