* AccidentallyAccurate: How accidental is up to debate, but the show's version of Dracula is actually pretty accurate compared to the original novel, especially in terms of appearance. They even got the DaywalkingVampire thing right!
* ActorAllusion: In the two-part episode, "Brown Evil", Billy mistakes Hoss Delgado for a wussy video game character named Pat the Baker, both of which are voiced by Deiderich Bader.
** Dean Toadblatt's voice actor is John Vernon, the same guy who played Dean Wormer in ''Film/AnimalHouse''. This explains why he yelled "Gunderstank House!" after getting pranked on the episode where Billy and Mandy go to a Hogwarts-style school for kid wizards.
** In the [[ChristmasSpecial Christmas Special]], the vampire Baron von Ghoulish, voiced by Creator/MalcolmMcDowell, is first seen filing his teeth and [[Film/AClockworkOrange singing Singin' In The Rain]].
** Two episodes feature Creator/KurtwoodSmith as Grim's dad, who is pretty much a skeletal [[Series/That70sShow Red Forman]] in terms of appearance and mannerisms.
* CastingGag: The Latin dub has a sort of one with Nigel Platter, as the VA that voiced him actually voiced Film/HarryPotter too.
** This isn't the first time Creator/PhilLamarr voiced a [[Franchise/MetalGear black vampire]].
* CrossDressingVoices: Irwin is voiced by Creator/VanessaMarshall, Pud'n is voiced by Jane Carr, and Nergal Jr. is voiced by Debi Derryberry.
** Irwin's grandmama Tanya is voiced by Creator/PhilLamarr.
* DescendedCreator: Maxwell Atoms voices Jeff the Spider.
* FakeBrit: Eris. What makes it funny, however, is that she's supposed to be a GREEK goddess. Furthermore, she also speaks like a ValleyGirl. Mainly, though, her mannerisms were meant to be a reference to {{Music/Madonna}}.
* KeepCirculatingTheTapes: The first season was released on DVD but that has long since gone out of print, the same can be said for Big Boogey Adventure's DVD, several episodes were released either on Cartoon Network Holiday Compilations or as extras on other [=DVDs=], thankfully the entire series (Sans Big Boogey Adventure, the Christmas special and Underfist) is available on iTunes. The show's first two seasons were also on Netflix, but are no longer there.
* OneOfUs: Fictional example. In the "Brown Evil" episode, whereas Billy prefers playing a cheesy cooking game named "Pat the Baker", Mandy prefers a much more violent ''Franchise/ResidentEvil'' parody featuring Hoss Delgado. At the end of the episode, Hoss states that he never leaves home without the former example and is seen cheerfully playing it alongside Billy.
** One episode, directly after the title song, has Mandy say, [[{{Film/Freaks}} "We accept you. We accept you. One of us."]]
* TheOtherDarrin:
** Creator/DavidWarner was the original voice of Nergal, but was later replaced with Martin Jarvis.
** Dean Toadblatt was voiced by John Vernon in his first three appearances, but due to his death, in "Nigel Planter and the Order of the Peanuts", Vernon was replaced with Ronnie Schell, who gave Toadblatt a much different hillbilly-like attitude. The change was lampshaded by one of the students at Toadblatt's, and the change may have been used to make reference to the fact that the same thing had happened with Albus Dumbledore in the ''Literature/HarryPotter'' films.
** Creator/WayneKnight was the original voice of Jack O' Lantern, but in the video game, he was replaced with Creator/MauriceLamarche.
* TalkingToHimself: There are a few examples in the series:
** Billy and his father Harold are both voiced by Creator/RichardStevenHorvitz.
** Grim and Sperg have a few scenes together throughout the series; both of them are voiced by Greg Eagles.
** Irwin's family is full of this. Irwin's dad, grandmother, and grandfather (Dracula) are all voiced by Creator/PhilLamarr. Creator/VanessaMarshall voices Irwin's mother and Irwin himself.
* ThrowItIn: Greg Eagles originally intended to voice Grim with a Swedish accent as a ShoutOut to ''Film/TheSeventhSeal'', but it accidentally came out sounding more Jamaican and they decided to just go with that because it sounded funnier.
* WhatCouldHaveBeen: The ''Underfist'' movie was meant as a possible pilot for a new spin-off series (made a bit more obvious due to the new animation style), but Cartoon Network turned it down. Some sources say that the creator, Maxwell Atoms, pitched the idea as a prank. Atoms confirmed in his interview with WebVideo/RebelTaxi that the rejection was due to changes in network heads.
** Grim was initially to have a British accent and a personality similar to that of [[Series/LostInSpace Dr. Smith]], even right down to being voiced by Creator/JonathanHarris himself!
** In the episode "One Crazy Summoner", when Billy's parents are attacked by a giant anaconda, Billy's dad says the snake is trying to eat his Bismarck. Considering the fact that ''Billy and Mandy'' is famous for GettingCrapPastTheRadar, this one sticks out.
** In [[http://67.media.tumblr.com/b473205cd2303022605138153040e6ba/tumblr_nywqlpEoLG1r2qm9ko6_1280.jpg the early bible designs]] for the series, Mandy looked ''completely'' different. Her eyes were pinpoints like Billy's, and instead of [[AnimeHair her signature blonde hair shaped like devil horns]], she was actually going to be a [[FieryRedhead redhead]] with [[GirlishPigtails a hairstyle very similar to that of]] [[WesternAnimation/ThePowerpuffGirls Bubbles]].
*** Both Billy and Mandy's personalities were different at the time too. Billy was less stupid and instead more shy and gullible, while Mandy was a creepy PerpetualSmiler GenkiGirl. In Atoms' college short film, Billy is actually smarter than the final product while Mandy initially seems nicer...but then she tricks Billy into drilling a hole into his skull, which prompts him to give a [[FridgeHorror big stupid grin]].
** For the ''Codename: Kids Next Door'' crossover, Mandy was originally going to torture Numbah One by forcing him to watch ''WesternAnimation/SheepInTheBigCity''. But CN's legal dept. feared that ''Sheep'''s creator, Mo Willems, wouldn't find it funny (as he was still working on ''KND'' at the time), so they had to clear it with Willems himself. He had no issues, but the legal guys still said no. So they tried changing it to ''Evil Con Carne'', but the legal team said no to that too, for whatever reason. So instead we had Fred Fredburger torturing Nigel.
* YouLookFamiliar: Creator/DiedrichBader as Hoss Delgado and Pat the Baker (a wussy video game character that Billy likes). Lampshaded in "Brown Evil", when Mandy and Grim say, "it's Hoss Delgado!" while Billy yells, "It's Pat the Baker!".
* The show's Indian rights is with Cartoon Network India which does not air the original English version of the series.They first aired the series under the name-"Billy Mandy Aur Life Main Haddi" which was not a success. Then in 2014 they re-aired the show under the name-"Haddi Mera Buddy" which went on become the second most viewed show on Cartoon Network India. In this one they air Indian English version where it is dubbed by Indian dubbing artists.
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