In "Any which way but Zeus", Doc Venture wants desperately to be kidnapped by the mystery villain and says this:
Dr. Venture: Soon this guy will want a "Rusty Venture" on his mantleplace
We later learn in "Operation PROM" what that means.
Dermott's posturing and sass during his first onscreen appearance becomes slightly funnier when we realize he was back-talking the man he thought was his father.
Dr. Orpheus being mistaken for a "Dracula" is even funnier after Hotel Transylvania was released, centering around the actual Dracula as a Large Ham single dad protecting his Perky Goth short-haired daughter from her dorky love interest. It even earned the nickname "Dr. Orpheus: The Movie" from some fans.
Fans had been crossing over Team Fortress 2 with Venture Bros. for a couple of years due to their similar art style and humor. Now there's VB Cosplay items in TF2, and an ad for the game even ran at the end of S5E1. Perhaps as a coincidence, that episode revealed that Sgt. Hatred's real name is Courtney, while TF2's resident Drill Sergeant Nasty also has a feminine name: Jane.
In season five's third episode, Shore Leave in a fit of exasperation yells "That's So Raven!" becomes funnier when the actress herself, Raven Symone, came out on twitter
"Well, did you dab?" "What?" "Dab. Did you dab?" "Uh...no?" "I dab." "Well, I don't." "You should dab." "Stop saying dab!"
One episode has Expies of the Scooby gang break in to the Venture compound to hunt a ghost they believe is there. It...does not end well for them when they go after the boys. Luckily, the gang's next encounter with Dean and his brother goes much more pleasantly for them.
Speaking of which, said series also has their Dean go through a montage where he ends up dying in increasingly darkly comic ways.
Professor Impossible's turn to villainy, spurned in part by rejection from his longtime romantic partner Mrs. Impossible, happened months before the same thing happened to the Mr. Fantastic and Susan Storm of the Ultimate Marvel setting.
The whole "Dr. Venture cloning Dean and Hank to keep them alive" thing, given a similar thing ends up being a plot point in explaining resurrections in X-Men (2019).
The episode "¡Viva los Muertos!" features Expy characters based on the Scooby-Doo gang crossed with infamous American criminals, including a cross between the show's Fred Jones and the serial killer Ted Bundy. In 2019 and 2020, Zac Efron would appear in twofilms where he played first Ted Bundy and then Fred Jones. Evidently the resemblance between the two goes beyond the imagination of this show's writers.
An offhand gag in "Self-Medication" has Rusty surprised that Action Johnny apparently scored with Velma, assuming that she was a lesbian. Come 2022 and Trick or Treat Scooby-Doo!, she is in fact gay.
In "Bright Lights, Dean City" Rusty starts composing a Broadway musical based on his life, and when the Brown Widow (the Venture-verse version of Spider-Man) likes the music, Rusty declares his intent to cast the hero in the show's lead role. The year after the episode aired, Spider-Man: Turn Off the Dark, a real Spider-Man musical, opened on Broadway. However, the production became notorious for difficulties like actors getting injured in stunts, and eventually closed at a huge financial loss.
