Occasionally a character would scream like this (one famous example is used as the page image here). Depending on the situation, they would either have Billy West or John Kricfalusi do it themselves, or dub in an inappropriate female Stock Scream. Lampshaded once, where Stimpy actually says "Scream like a girl!" while doing so.
Stimpy can pull off a very good one in the German dub. If there was a "pitch human speech was never meant to reach", this would be it.
On The Venture Bros., Dean Venture screams like a girl in the episode "Love Bheits", prompting a eunuch to quip "I'm fixed, what's your excuse?"
Duckman's scream has, on occasion, sounded exactly like a little girl.
The earl of Lemongrab doesn't scream like a little girl so much as he screams like a schizophrenic woman on her menstrual cycle. Okay... He screams like that pretty often, due to his high, uber-puberty voice.
Finn also screams that way when he's startled. Like in the episode "Burning Low" when he's about to leave the Tree Fort to see Flame Princess, only to see Princess Bubblegum at the door.
In "Evicted!", this occurs to Jake after their window opens suddenly.
Finn: It was just the wind, scaredy cat. Jake: I wasn't scared! I was singing! I was singing my "scream song". WAOH...WEAOH...WEAAAAOOOAH. Finn: You're a total wuss, man.
When Disneytook overDoug, it became rather obvious that Roger Klotz now had someone else providing his voice whenever he screamed in terror. While (in the Nick series) the title character didn't scream like a little girl, he sure did have a high-pitched scream!
When a massive stack of metal falls on him in the episode "Autoboot Camp", Sentinel Prime screams like a little girl.
So does Grandus, when he encounters the "scary organic" Captain Fanzone in "This is Why I Hate Machines". For some perspective on that last bit, Grandus transforms into what looks like one of those vehicles they use to carry the space shuttle around, and is the Autobot equivalent of a sumo wrestler.
Skywarp does this when he sees that Prowl has caught up to him after attempting to escape him and Lockdown.
Soundwave in the original cartoon. Given that he's supposed to be a cold, heartless Decepticon, it's surprisingly hilarious.
In the Transformers Prime episode "Scrapheap", Bulkhead lets one out when the lights go out, and Miko makes fun of him. Miko then lets one out when she freaks out over a spider. She IS a little girl though, so it's okay for her.
Almost any incarnation of Starscream, especially when confronted with something painful.
Space Ghost Coast to Coast: Space Ghost took this one step further. The body snatcher pods arrived, and he screamed once. Trying to leave the building, he finds it's been covered by the monster from The Blob (1958); another scream. Then, he flies back into the studio and babbles incoherently in a little girl's voice before clearing his throat.
Bender does this when Roberto tries to stab him in "Insane in the Mainframe". Bender also screamed in Leela's voice while under the influence of the emotion chip in "I Second That Emotion", when El Chupanibra was about to eat Nibbler.
Fry did this a lot, especially in the episode, "Roswell That Ends Well", when, after traveling through time, ending up in Roswell, New Mexico, he sleeps with his grandmother, and inadvertently becomes his own grandfather.
Coop: Jamie, quit screaming like a little girl! Jamie: It's not me, dude, it's him. (points to driving instructor, who screams again) Coop: Oh. You, quit screaming like Jamie!
Odd Della Robbia, a few times in Code Lyoko. Notably at the end of episode "Guided Missile". Ironic since he's dubbed by a male voice actor, unlike other young boys in the series who have Cross-Dressing Voices.
The Mayor does this for several seconds in an early episode.
Mojo Jojo also does this in "Meet the Beat-Alls" when he discovers Moko Jono's true identity.
ReBoot: Bob, Dot, Enzo and Mike the TV get trapped in a Dungeons & Dragons type game and come across a giant spider. Cue high-pitched scream. Bob looks at Enzo. Enzo looks at Dot. Dot shrugs and points at Mike (the source of the scream).
Ben 10: Alien Force After Ben sees a television advertisement for Sumo Slammers the motion picture, he does this in a very fan-girly way.
Rank's Camera Man: Rank may not know how to treat little girls, but he sure knows how to scream like one!
A young Valmont lets one out in the episode "Through the Rabbit Hole".
General Skarr from The Grim Adventures of Billy & Mandy as part of being the world's Butt-Monkey, most notably in one episode where he is caught on fire by Grim's scythe in his vain attempts to prevent Billy from destroying his beloved garden, where he continues to screech until Grim puts the fire out by stomping on him... poor guy never catches a break.
Billy is also capable of screaming like a girl, especially when around bugs.
Mr. Bogus often screams this way, most of the time.
Stu Pickles also has a rather girlish-sounding scream on Rugrats (making chocolate pudding at 4 AM, anyone?).
Many male characters in Total Drama tend to scream like this.
In Garfield's Halloween Adventure, Garfield and Odie both scream like this during the song "Scaredy Cat", whenever they come across a trick-or-treater who is not what it appears to be. This doubles as Hypocritical Humor, because just before making the discovery, Garfield continuously sings that he may be a lot of things, "but the one thing I'm not is a scaredy cat."