Hilarious In Hindsight / The Grim Adventures of Billy & Mandy

• In one episode, Grim is seen watching a My Little Pony parody called "My Troubled Pony" and enjoying it very much, in spite of the fact that he's a male adult and he's clearly not within the show's demographic. Fast forward to 2010...
• Nergal is a tall and thin Humanoid Abomination with Combat Tentacles and wearing a suit. Almost eight years after his debut, a very similar character with no intentional connection to the show (per statements by the creator) would achieve widespread popularity online.
• In the beginning of Big Boogey Adventure, Billy doodles "cops fighting dinosaurs" instead of writing out plans, and then remarks that "they should be working together" when Irwin calls him out. It wouldn't be the last time that concept came up.
• Monster High came out with a line of dolls called "Freaky Fusions", complete with an animated movie based on them. Obviously, the premise is based on Hybrid Monsters. It becomes funny when you realize that Maxwell Atoms already did this with the aforementioned Irwin. (Good thing they didn't do a mummy/vampire, otherwise he'd probably sue...)
  • In a reverse of this, the anime Kinnikuman featured a wrestler named Mr. Khamen, whose theme was simultaneously vampires and Ancient Egypt (including a move that mummifies the opponent).
• Hoss Delgado has an eyepatch, a robot arm, a mullet and fights Grim who obviously has a skull for a face due to being a skeleton. Come 2015 where a a certain game features a protagonist with a robot arm, mullet and eyepatch fighting a character named Skull Face. Cue Hoss Delgado is Venom Snake◊ comparisons.◊ Doubly hilarious since Grim himself is voiced by Greg Eagles, who had previously voiced The DARPA Chief, Gray Fox and Peter Stillman.
• In the video game, Dracula and Irwin's victory quotes when beating each other become this (or maybe Harsher in Hindsight, depending) when you realize Dracula is Irwin's grandfather.
  Dracula: Dracula need yo glasses! Dracula not seeing so good no more.
  Irwin: No! I'm allergic to vampires!
• In one episode, Billy wears Junior as a magic pair of pants to help pass a fitness test. (It Makes Sense in Context.) As pants, you can still tell it's Junior because he still has his eyes (and glasses). Hm, people wearing magic clothes with eyes... Why does that sound familiar? (Tumblr's certainly caught onto this one.)
• This wouldn't be the last time Nika Futterman voiced a depiction of Pandora.
• In "My Fair Mandy", Mandy (sort of) sings "Somewhere Over the Rainbow" for the talent portion of the contest, complete with set and costume. Grey Delisle, who voiced Mandy, would later star as Dorothy and sing the same song (for real, not like the annoyed way Mandy was performing) in Tom and Jerry and the Wizard of Oz.
• Billy's irrational fear of clowns (along with "DESTROY US ALL!!!") is becoming this with reports of creepy clown sightings in real life (can combine with Harsher in Hindsight as well).
• In the pilot episode, the toy monster Billy plays with has a head that's nigh-identical to that of Eelektross.
• In Hoss Delgado's introduction episode, Grim revives a bunch of dinosaur skeletons and makes them dance. Harry Dresden does the same.
• The Brain-Eating Meteor from "Little Rock of Horrors" has a very similar appearance to Omni, the Greater-Scope Villain of Power Rangers S.P.D..
• In the Latin American Spanish dub, Mandy is voiced by Rebeca Gómez. It wouldn't be the last time she'd voice a ruthless girl with blonde hair who's friends with a psychopomp.
• In "One Crazy Summoner", Dean Toadblatt is doused with a love potion and falls in love with the Squid Hat. This episode came out in 2005, and Professor Dumbledore (who Dean Toadblatt is a parody of) was said to be gay in 2007.
• The Running Gag that saying Moldybutt's name causes destruction is a parody of Potterverse wizards' reluctance to say the name of Lord Voldemort. In Harry Potter and the Deathly Hallows, Voldemort actually does put a jinx on his own name (granted, his version is a little more serious, but still).

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