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It's actual irony, I guess. You understand that it's a guy trying to call a girl he likes. He's not able to do it right though and so just sounds like a murderer.

I guess, that's the joke. Why is it funny? I don't know. Comedy is hard. Go watch Norm Macdonald a bunch and ponder what it means to be a great comedian.

Will you go there?

I think the thing that makes the joke funnier is that Hailey doesn't just take the phone away from Klaus. It's just a hard cut to her smashing the phone. It was just that bad.

Danuta

Because you think he’s going to blunder calling his crush in some relatable way but the show subverts that expectation by making his nervousness sound like a slasher villain call

It's 100% Klaus delivery. Like a lot of the jokes from, let's say for example Aqua Teen Hunger Force, it's an okay joke that's carried by the stellar performance of the voice actor.

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it's funny because the delivery is spot on.
he just fucks it up so bad in a hilarious way, obviously no one would sound like that talking on the phone but klaus manages to do it and make it sound menacing.

my second favorite klaus moment. my favorite one is the one in the Obama episode where the secret service shoots him jumping out of the pool and he explodes into gibs

Best Klaus moment is "I killed them all".

Rarely have I ever witnessed a joke this fucking flat.

My favorite one is the song he wrote about Hillary clinton

Pizza OverlordKlasuwrotethelyrics