In "Vampires and Robbers", when the two robbers first see Klot, we get this line:
Lefty: Ah, he looks like a little Mexican sailor!
Any time a vampire exclaims "By Dracula's overbite!" or Polidori with "Van Hellsing's left hernia!". Count Von Horrificus also throws out a "Garlic-buttered gravestones!" in one episode.
Stoker acting as both the prosecutor and witness in "On My Honour, Your Honour" counts as one, especially when combined with his huge ego and over-the-top acting.
In "Topsy Turvy", Oskar, while having swapped bodies with Stoker, repeatedly yells "Say no to blood! Blood! Blood!" while being dragged off by his friends. The handful of awkward pauses in the English dub make the scene all the more ridiculous.
Count Von Horrificus attempting to escape from Polidori's cage while being stuck in bat form in "Blood Relatives":
Count Von Horrificus: Perhaps it would help if I transformed back into my normal form! (He transforms, but his normal form barely fits in the cage)...On the other hand, perhaps it wouldn't.
When he and Gothetta first encounter the troll in "Troll Ahead", Stoker delivers this line:
Stoker: Take the girl! I have a great future!
The entire concept behind "Zoo Time" is that Count Von Horrificus gets captured while in bat form and taken to a zoo while Oskar and Klot have to go rescue him. Made even funnier when a female bat repeatedly tries to hit on the count as he tries to discuss an escape plan with Oskar.
Count Von Horrificus: Hypnotize the infant and get me out of—Oh for Dracula's sake woman, leave me alone!
Stoker accidentally hypnotizing himself into thinking he's Abraham Van Hellsing in "Transformer" and repeatedly and hilariously failing in his attempts to stake the other vampires.
The episode "Super Klot" is full of funny moments, as Klot defeats the villain of the day by dressing up in his own handmade outfit of his favorite superhero, Super Fiend, and discovering that the villain's henchman also loves that superhero, leading the henchman to befriend Klot and dress as Super Fiend's sidekick and fight his former boss with Klot. Made even funnier with the fact that Klot is a teeny child and the henchman is a big burly guy. We also get these lines from Gothetta upon her seeing their superhero masks right around the final showdown:
Stoker: What the Drac is going on here? Who are these lunatics?
Gothetta: Are those my stockings?!
Villain: [to his henchman] What are you waiting for? Get them!
Gothetta: They are my stockings!
In "All Work and No Play", the kids make a helium-inflated cow costume for use in a school play. They end up using it to sneak into the town during the daytime. Hilarity ensues. The townspeople are understandably gobsmacked when they see it, but Polidori is completely unfazed.
In "Home Alone", the kids don't like Lenny's new recipes but don't know how to break it to him. Stoker, deciding that he has "the most impeccable manners", tells Lenny that his new cooking "would poison a cave troll". And then there's Lenny's response:
Lenny: Fine! Cook for yourselves then, see if I care! (Beat) And the cave troll was an accident, nothing more!
In the episode "Superstition," a fortune-teller predicts for Gothetta that she'll meet a tall, dark man that looks like a young Johnny Depp. Stoker naturally assumes that means him.
In "The Vampire Hunter-Hunter," the eponymous Vampire Hunter Hunter sends vampire hunters to an always-sunny tropical island where there are no creepy castles for them to snoop around in nor any vampires to hunt. The hunter-hunter also throws out a line later on threatening to get Oskar if he ends up reading about his secret weakness getting leaked or "seeing it in a film or, say, an animation show on TV".
"A Vampire's Kiss", which features hijinks caused by love potion gone awry, has a lot of funny moments and is probably one of the funniest episodes of the series. This exchange is just one example that stands out:
Stoker: [to Sunshine] Don't fight it cheesecake, that feeling in your chest — that's not indigestion, that's love.
Sunshine: Okay, you'd better go now. No offense, but you're weird, and my grandpa doesn't like weird, which is weird, because, well, he's kind of weird!
Stoker: No! Don't leave me! If I had a heart, it would be breaking right now! Wait, please take this. (hands her a heart-shaped cookie)
Sunshine: What is it?
Stoker: (melodramatically) It's my heart. I won't be needing it anymore!
Sunshine: (with annoyance) It's a cookie!
Stoker: You want it or not!?
Count Von Horrificus reuniting with Klot's father, his old school friend, in "Father's Day". Immediately upon meeting each other, both scary-looking adult vampires do their old chant and secret handshake from when they had been kids in school.