When he finally got it, it bugged him. It sounded like a transgender gag because he didn't include the middle name when trying to get the attention of the one he thought might be in there. It wasn't even a phone call because the whole thing was set during the middle ages, but it was a gag.
Take care and God bless

Btw, I watched The Simpsons last night and I didn't like it. The part your talking about, I think, was when the only time I laughed.

It's not the funniest idea for a prank call to Moe's gag that I've heard, but it's obviously gonna have to do for awhile. I thought Oliver Closeoff was a better gag even though it took me years to get it. Bea O'Problem is another one. I'm trying to remember the one he made and then lied about it being the bully Jim who made it. I like the one word name I came up with pretty well. It amuses me, but I don't know about anyone else.
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There was B.O. Problem, Ivana Tinkle, Hugh Jazz(which was just on, btw), Myra Buttreeks, and others.

The third one isn't one that I'd repeat because to use that word to mean anything but donkey is considered swearing like the one with Hugh implies. I believe Maya Buttwreaks is the way it should be spelled, and that was on a list of people in the class that Bart probably used to substitute the real list. The other one from that list is Anita Bath. After those two, Moe just decided he didn't want to be a substitute teacher. At first I thought maybe Moe mispronounced Mia, but then I used closed captions for another where Bart's prank calling other bars and makes a call to Hawaii to ask for Maya Normousbutt. I don't believe that I'd care to repeat the one where he's asking for a Mike with the last name Crotch either. It gets a laugh, but I wouldn't go repeating it. Amanda Hugnkiss is the one I'm thinking of in the episode that also uses Ivana Tinkle; and if that's the one, it's Amanda Hugnkiss that the bully got the blame for.
Take care and God bless

There was B.O. Problem, Ivana Tinkle, Hugh Jazz(which was just on, btw), Myra Buttreeks, and others.

On thesimpsons.com's character profile section of Moe, it says that Bart prank called him and asked for Mary Mebarney.

When was this?

It took me a few seconds to get that one. I watched the episode where he calls to ask for Hugh; and that's one that backfired on Bart because there really was someone by that name, so he didn't get his laugh on Moe with that one. The one in the premiere episode for this one is too new, so that's why I haven't revealed what it is. He did ask for the prank call in the one with Hugh in it because he had stolen Homer's drink and was marketing it for himself.
Take care and God bless