Most of the love songs on The Amazing Chan and the Chan Clan are like this, but in a cute harmless way. Plus, they also seem meant to make use of the show's detective theme with titles such as "Undercover Man" and "Whodunit" so it's partially justified.
The Creeper has a short yet extreme crush on Harley Quinn that causes at least one The Cat Came Back-like moment. Though we actually see him sniffing his way through the town, trying to follow her.
The Mad Hatter's creepily stalkerish behavior towards Alice!!!
Terry/Batman's girlfriend Dana gets one in an episode of Batman Beyond, though at first she thinks that the flowers and notes are from Terry himself. She doesn't take too kindly to being kidnapped, no matter how conscientious her captor is, then she finds out that she's not the first person he's stalked.
Magpie to Batman in Beware the Batman. Though it initially starts as mild attraction towards him in her first appearance, she becomes obsessed with him when he pays visits to her prison to make her feel less miserable. In "Attraction", she mistakes his partner Katana with his lover, and she breaks out to try to "rescue" Batman from her.
Lorna from Carl Squared. Complicated by the fact that Carl's clone C2 is a little sweet on her.
Chowder: Panini definitely qualifies as Chowder's stalker. She watches him with binoculars, physically chases him around, wanted to have him legally declared her property, and for a brief period lived in his clothes.
Elisabeth "Sissi" Delmas from Code Lyoko stalks and harasses Ulrich, her "sweetheart", almost every day, and is close to obsessed with finding out the Gang's secret. It gets to the point where, in the last episode, she goes as far as to attach a tracking device to Ulrich's coat (no word on where a fourteen-year-old schoolgirl got a tracking device, probably the Internet) to find out where he and his friends disappear to every day. It does work, but the trusty RTTP is there to reset it. The ex-Lyoko Warriors finally accept her as a friend after that to thank her for all the help she can't remember giving them, so we can assume that the obsessive behavior has stopped.
To some extent, William towards Yumi, though he's not nearly as obsessed. Only creepy. Especially as he never appears to hang out with or talk to anyone else on such a regular basis.
King Sandy in "Operation: B.E.A.C.H.", who wants Numbuh 3 to be his queen. He abducts her and is nearly able to force her to marry him (they're kids!) before Numbuh 4 rescues her.
Fourth grade class president Jimmy Nixon McGarfield in "Operation: S.N.O.W.I.N.G.", who is infatuated with Numbuh 1's girlfriend Lizzie Devine. He even uses mind control to try to make her fall in love with him. He would have been successful had his assistant Anna (who had her own crush on him) not sabotaged his plans. When Anna tells Jimmy she is in love with him, he subsequently returns her feelings, abandoning his fixation on Lizzie. Considering some recent developments, it's a good thing he did, for more reasons than one.
Vlad Masters/Plasmius in Danny Phantom fits this trope. It doesn't matter that Maddie is happily married with two children to Jack. He also has the trappings of this with Danny, though it's more a platonic than romantic (Sorry shippers...) which makes it creepier.
Ed, Edd n Eddy: The Kanker Sisters (the three trailer trash girls Lee, May, and Marie) towards the the Eds in a very over-the-top fashion. It's still unknown whether or not they actually genuinely care about the Eds, or just want men to boss around and do their chores.
Timmy has Tootie, who is fairly sweet otherwise, but she comes on too strong for Timmy (possibly coming from the fact that Vicky is her older sister). Tootie's attitude ends up so overbearing to Timmy that in "Kung Timmy," he actually places a restraining order on her.
Juandissimo, who is in love with Wanda, despite the fact that she is married to Cosmo.
Also, The Darkness in "Wishology" becomes obsessed with Timmy after he becomes the first person to put something good into it (i.e. light). In fact, all its action in Parts II and III were to capture him and keep him close to its heart... It wipes out Yugopotamia and captures a race of creatures just to do this.
Herbert. He could just be a creepy pedophile, though... His attentions aren't always spent on Chris, though Chris seems to be his main target.
Meg in the episode "Barely Legal" where she became violently obsessed with Brian after he took her to her prom, which included making a Stalker Shrine.
There was a one-shot character that happens to be Peter' old prom date, who has a hallway full of pictures of Peter. She is also wearing the dress that she wore to that prom...and hasn't washed the hand that touched Peter's since then...or flushed the toilet he used either, for that matter. Her explanation of everything is "It's a little piece of you that's kept your memory alive!" Squick Central...
Quagmire may hit on anything in a skirt but there are a few episodes that portray him as having an unhealthy obsession with Lois (despite that in "Jerome is the New Black," he names off "hitting on Lois" as one of the reasons why he hates Brian. Hypocritical Humor, much?).
To some extent, there's also Neil Goldman towards Meg.
The episode "Peter-assment" portrayed Peter's boss Angela as being one of these towards him.
In Foster's Home for Imaginary Friends, Berry's stalker-ish crush on Bloo becomes quite extreme, to the point she even tries to get rid of Mac so she can have Bloo to herself. The trope is clearly lampshaded in a subplot where the rest of the characters are deeply engrossed in a soap opera with a love affair that goes sour.
Hey Arnold!: There are several hints that Helga's comedic stalker, Brainy, followed her around because he had a crush on her. In the one episode when, instead of punching his lights out, she finally asked why in the world he's always lurking behind her (and how he finds her), his only response was "I like pain." to give her a ring.
But that's nothing compared to Helga herself. She has a shrine, a bubblegum statue made out of his chewed bubblegum, and several books of poetry dedicated to Arnold, even though she treats him as badly as she treats Brainy.
In the episode "Ernie in Love" the titular Ernie sees, falls in love, and stalks a woman named Lola. Though he does go on a date with her, and stops being Stalker with a crush to an acquaintance without a crush.
Many of the things Ernie does before getting the courage to talk to Lola mirror the things Helga does, including making a statue of her and writing multiple love poems.
And then there's Curly towards Rhonda.
Heloise in Jimmy Two-Shoes. The actual stalking part is largely not seen, since she's already friends with Jimmy, but she does have a Stalker Shrine hidden in her house. A one episode gag had Jimmy saying her name, having her pop out of a bush holding binoculars, the clear implication being that she was watching him.
Heloise herself has a stalker in the form of Peep.
In Justice League Unlimited, Carter Hall believes that he and Hawkgirl are destined to be together because they're the reincarnation of Thangarian lovers in ancient Egypt. Even though this is strongly hinted to be true, he still comes across as a Stalker with a Crush. Most of the Justice Leaguers (Batman and Green Lantern in particular) have not failed to notice this.
The "reincarnated Thanagarian lovers" thing is also subverted when it is revealed that proto-Hawkgirl ended up leaving proto-Carter for proto-Green Lantern. Yep, even destiny itself is telling Carter to buzz off.
Pretty is obsessed with Mr. Cat and constantly takes pictures of him on her phone, intrudes his personal space and randomly shows up and follows him, but there are implications that she only likes him for his body.
Mr. Cat himself starts becoming one to Kaeloo as the series goes on, and he starts doing weird things like taking pictures of her butt and putting them on a calendar or breaking into her bedroom to sleep in her bed.
Kaeloo can be one to Mr. Cat Depending on the Writer, such as the fact that she apparently texts him nonstop whenever he's not physically in the same place as her. Mr. Cat even notes that it seems like she's "crazy about him". Not that he minds.
Wackie Jacky from Kick Buttowski is this to Kick. Complete with a creepy room filled with his pictures.
Kim Possible once spent an episode stalking Ron and Yori in their mission, due to her crushing on Ron and being jealous of Yori (a jealousy that included accusing Yori of being the Enemy of the Week).
DNAmy is definitely this towards fellow villain Monkey Fist.
Unlike the video games, where his obsession seems to be solely with her power, Ganon seems to have some attraction of this nature toward Zelda herself in the animated Legend of Zelda. In one episode he abducts her and tries to force her to marry him; in another he declares to his minions, "I want that princess!"
Russell from Littlest Pet Shop (2012) is temporarily brainwashed into falling in love with Penny Ling, and does it to the extremes that's he outright terrifying (Think Pepé Le Pew on crack) The same thing later happens to Vinnie for Minka, and Sunil for Pepper respectively.
Looney Tunes: Pepe LePew — and it doesn't matter if the cat is male or female (and 1947's "Scent Imental Over You" showed us that it didn't matter if it was a cat, because the object of Pepe's affection in that short was a chihuahua who glued skunk fur onto her body so she can be like the other dogs), so long as she (or he) is painted like a skunk. And the DC Comics version of Looney Tunes had Pepe go after a black bull (the one who squared off with Bugs on "Bully for Bugs") with a white stripe and several human women who in one way or another have black and white skunk stripes on them. Can we say "Anything That Moves," boys and girls?
Pepe: (at the end of "Little Beau Pepe") Why is it that whenever a man is captured by a woman, all he wish to do is get away?!
In the Bugs Bunny cartoon, "Rabbit Romeo", Millicent an overweight and ugly Slobbovian rabbit is like this toward Bugs. Bugs is eventually able to turn the tables and steer Millicent onto her caretaker Elmer Fudd!
Ironically, when Lola's attention switches to Daffy, Bugs starts being attracted to Lola, and unwittingly plays along when she attempts to use him to make Daffy jealous.
Miraculous Ladybug: Marinette (of all people!) has stalking her crush down to a science- literally, a detailed schedule based on her analyses of his life, having as well an actual shrine of him by filling one of her walls with his photos, stealing his phone and so on. In "Party Crasher" she literally dresses up as a boy so bodyguard would let her come into his house where he was hosting a boys' night. In "Chat Blanc", she sneaks into his room and throws herself into his bed...honestly, she's far beyond cute and straight-up creepy
The episode "Pixelator" offers a visual contrast with another stalker. "Volpina" also deals with Marinette's stalker tendencies, with her apparently learning her lesson after harshly calling out Lila for her lies, blinded by her love for Adrien.
Before they became an Official Couple, Candace was something of this to the oblivious Jeremy. At one point she was even spying on him with binoculars (yeah, ok, from a few feet away, but still). Candace even realized this in the first movie and stopped herself shortly before she and Jeremy hooked up.
Even though they're friends, Isabella is also like this with Phineas. The only usual reason she sees/helps/hangs out with Phineas and Ferb and go though their adventures together is only to get Phineas' attention (and to a much lesser extent, badges).
Buttercup in The Powerpuff Girls episode "Buttercrush." Her pining for Gangreen Gang leader Ace nearly doomed her sisters.
He didn't seem to mind it, and used it to his advantage—hence the "nearly dooming her sisters" part.
Katrina Rad in The Problem Solverz episode "Magic Clock". She starts out as a Loony Fan for the trio, but while following them around to write a blog entry about them, she escalates into a crazed Roba fangirl.
Katrina: Mm, Roba's shadow is so good lookin'... I'm gonna hug it!
Roba: Okay, now I'm really creeped out.
Ready Jet Go! has a rare example in which both the stalker and the crush are this to each other. Mitchell is the stalker first. In his debut episode, "Mindy's Moon Bounce House", Mitchell watches Mindy, his (speculated) crush through a pair of binoculars. Later, in "Solar System Bake-Off!", Mitchell attempts to spy on Mindy and her baking contest entry, and acts rather awkward around her. Mindy then becomes the stalker starting in "What Goes Up...", where Mindy sneaks up on Mitchell several times throughout the episode. It would then become a Running Gag which would appear in "Kid Kart Derby" and "Detective Mindy", where Mitchell more or less warms up to her. Then in "Mindy's Mystery", Sean and Sydney actually more or less help Mindy to stalk Mitchell! (Then again, all they were doing was trying to track the source of the mystery smell from Mitchell's yard)
Hexadecimal of ReBoot sometimes acts this way towards Bob.
Ogo toward the titular Robot and Monster. He has done things such as taping pictures of Robot to the back of his eyelids so he sees him whenever he closes his eyes, and making a pillow out of Monster's fur.
Artie Ziff was this way to Marge in the later seasons.
"I am watching you THROUGH A CAMERA!"
Moe Syzlak stalked Marge and other Springfield women; one of them placed a restraining order upon him.
One-shot character Julia was one of these towards Homer in the episode "Homer Of Seville".
Comic Book Guy has a restraining order from Lynda Carter.
In later seasons, Milhouse was badly Flanderized into becoming this for Lisa, becoming one of his defining traits alongside being a wimpy Kiddie Kid. Starting in Season 29, he also becomes one for Maggie, despite her being a baby.
Venom in The Spectacular Spider-Man, but it's a bit of a Love Triangle. The symbiote wants to be with Peter Parker, who it is mad with for rejecting it; host Eddie Brock is also mad at Spidey, but he teams up with the symbiote because he thinks it's the only one left that cares for him, even though he admits "it only loves me for the hate". In Brock's case it could be particularly bad because, since he knows all of Peter's secrets, he should also know why Peter appeared to act so irresponsibly and selfishly- he was in reality either busy as Spider-Man, or himself being corrupted by the symbiote. But he still feels alone so he keeps going back to the symbiote just so they can hate Peter together.
In 1990's Spider-Man: The Animated Series there's Hydro-Man. The guy only ever shows up to chase Mary-Jane around. He was so obsessed over her that after his clone heard she may have died he forced Dr. Miles Warren to create a clone of her based upon his abilities. Didn't really work out for him; as she still loved Peter and they both died anyway.
SpongeBob SquarePants: The episode "That's No Lady" has Patrick dress up as a girl named "Patricia", leading Squidward and Mr. Krabs to fall in love with "her" and act like complete stalkers, popping out of random places (like the sink and the fryer) to ask "Patricia" out on a date. And they still persist even after Patrick continues to tell them "no".
In the episode "The Two Faces Of Squidward" the entire town act like stalkers towards Squidward after an accident causes him to become very handsome.
SpongeBob's Ho Yay-ish actions towards Squidward carry undertones of this.
Donatello to April in Teenage Mutant Ninja Turtles (2012). He stares at her from afar, knows very little about her, and had spent hours making a chart on every possibility April will throw at him.
In Season 2, he still follows her after she yelled at him and his brothers for accidentally mutating her father. This stops once she goes back to them.
Sierra definitely qualifies as this to Cody, smelling his shoes, sucking poison out of him, and knowing everything about him to the point where he develops a phobia of her. This is mainly because she is a Loony Fan, as Heather has noted.
Chris: The things you know scare us. Seriously.
Izzy's biography claims she stalks boys that interest her. In one episode, she mentions an old boyfriend got a restraining order against her, and adds that he should get new blinds for his bedroom because she can't see anything through the ones he has. Apparently she's still stalking him.
Myra Brandish of The Venture Bros. is the insane former bodyguard of Rusty Venture who believes herself to be the mother of his twins (this is heavily implied to be true) who breaks out of asylums once a year to antagonize the Ventures somehow, still being in love with Venture and obsessing over her (supposed) children.
In the third season of Winx Club Nabu was a somewhat more benign version of this in the first few episodes he appeared in. He had run away from home in order to learn what the girl (Princess Aisha) his parents had arranged for him to marry was really like, and he ended up falling in love with her.
Wolverine/Logan comes across as this in a number of episodes from the '90s X-Men as he hopelessly pines for Jean Grey, who, despite being at least somewhat interested in him, is adamantly loyal to her boyfriend, team leader Cyclops.
The X-Men: Evolution version of Blob is this briefly, when he thinks that Jean's refusal to hang out with him is an insult (rather than simply that she has stuff to do).
Coop has the dig on for Yin in Yin Yang Yo!, though his becoming The Mole for the Night Master isn't entirely to please her so much as he's tired of being kicked around.