The Marvel Cinematic Universe is known for well written, dramatic monologues, as well as quippy one-liner jokes. The MCU also has a reputation for being appealing to audiences of all ages, usually opting for more general humor even the kids can understand.
Despite this approach, and initial concerns over the Disney acquisition, the MCU hasn’t shied away from more adult topics. These movies/series often graze up against some humor that would make adults blush and leave children confused.
Ralph Bohner - WandaVision
In perhaps the simplest and crudest joke to date in the MCU, in standing in for Wanda’s brother, Quicksilver, is just some random guy living in Agatha’s house, and his name is Ralph Bohner. There’s not much more to this - the joke is simply that this character’s name sounds like the term for an erection. While perhaps initially funny, this joke left a sour taste in the mouths of fans who felt strung along by the stunt casting of Evan Peters as Pietro.
“Can’t Get Too Excited” - The Incredible Hulk
The Incredible Hulk has an intimate scene where Bruce Banner and Betty Ross share a motel room and finally let down their emotional barriers and start getting hot and heavy. This is, until Bruce puts a stop to the whole thing, saying he “can’t get too excited.” This is certainly a question comic book fans have pondered about the Hulk - whether or not his affliction interferes with his sex life - but not one fans expected to have answered in a cinematic adaptation. Oddly enough it implies that Bruce cannot handle getting an erection without "hulking out."
“Fondue?” - Captain America
A running joke in Captain America: The First Avenger is “Fondue.” Howard Stark, entrepreneur and ladies’ man extraordinaire has a reputation for having women over for “Fondue,” which is suggested to mean doing the do. It’s even implied that Peggy Carter, Steve’s love interest, may have fondued or will with Howard. It comes to a point where Steve awkwardly asks, “are you two...do you...fondue?” It’s amusing to see The Star-Spangled Man with a Plan skirting around the issue of sex with the confidence of a flustered and bewildered boy scout. This joke, and the term “Fondue” even became a meme for some time amongst fan communities.
“Spread On Tony” - Iron Man 2
In ing character and love interest, Pepper Potts, responds that she re Everhart doing quite the “spread” on Tony, referencing their one night stand at the beginning of the first Iron Man. This joke is a fun burn, and one of a few instances of catty behavior coming from Pepper.
“Performance Issues” - The Avengers
Throughout The Avengers, Loki has been using his staff to mind control various people, including Dr. Selvig and Hawkeye. When he attempts to do this to Tony Stark, however, the staff fails to make through Tony’s Arc Reactor.
Tony Stark takes this opportunity to poke fun at Loki over his inability to mind control him, saying “well, performance issues, you know it’s not uncommon.” This is a more subtle dig coming from Tony, and a nice punctuation for this trash-talking moment.
“Not The Worst Thing You’ve Caught Me Doing” - Iron Man
In Iron Man, Pepper walks in on Tony as his armor is being stripped off him by mechanical arms. In a comedic beat, Tony says “let’s face it, this is not the worst thing you’ve caught me doing.” This could imply a lot of different things, but given Tony’s established history of being a bit of a playboy, it’s safe to say he’s referring to some off screen moment where Pepper unfortunately walked in on Tony in flagrante dilecto.
“The Old Fashioned Way” - Guardians of the Galaxy Vol. 2
Thanks to the touch of James Gunn, both Guardians movies are peppered with adult humor, and in Guardians of the Galaxy Vol. 2 it kicks in in the very beginning. In a very Captain Kirk from Star Trek move, Star-Lord begins flirting with Ayesha, the High Priestess of the Sovereign, after completing a mission for her. In a discussion over the nature of the Sovereign being genetically engineered, Peter Quill mentions he prefers to “make people the old fashioned way.” What’s surprising is how intrigued the High Priestess is at the prospect of engaging in an “archaic history lesson” with Star-Lord.
Thor See Hulk’s Junk - Thor: Ragnarok
In this scene in in the Strongest Avenger's room after his defeat in the gladiatorial arena on Sakaar. While in the middle of his bath Hulk gets up and absentmindedly strides over to the window, giving the God of Thunder a view of everything. Thor is visibly flustered, shutting his eyes and saying to himself “that’s in my brain now.” While the joke is mostly innocent, it still is on an adult subject, and is notably the third time Hulk’s downstairs is brought up in the MCU.
Ego’s Penis - Guardians of the Galaxy 2
While Starlord’s biological father, Ego, is explaining how he created the planet that is him as well as the body he appears before them as, Drax interrupts to ask if he made a penis. After some bickering amongst the group, he confirms that he does indeed have a penis, and even brags that it’s “not half bad” which is suitably in character for a being named “Ego.”
Dave Bautista really sells it as Drax in this scene, seeming genuinely offended when Star-Lord is grossed out by him talking about how his parents conceived him, griping that “Earthers have hangups.”
“Hide the Zucchini” - Avengers: Age of Ultron
Leading up to the third act of Age of Ultron, Tony drops this line casually, saying Bruce and Natasha “better not be playing hide the zucchini.” This line skirts between being explicit and subtle; it seems an innocent enough statement on its own but there’s not much else the term ‘hide the zucchini’ could mean, especially considering the obvious budding romantic relationship between the two. What’s more is the joke appears to be poking fun at the coloration of Hulk’s "equipment."
“Jackson Pollock Painting” - Guardians of the Galaxy
This one is possibly the grossest adult joke in the MCU. In Guardians of the Galaxy After Gamora comments on the filthy state of Starlord’s ship, Quill muses out of earshot, “if I had a blacklight, the place would look like a Jackson Pollock painting.” These words paint an unfortunate (or fortunate, if you’re nasty) picture of Peter Quill letting loose all over his spaceship. This also has a perhaps unintentional implication when coupled with the fact that his ship, the Milano is named after Who’s the Boss star, Alyssa Milano.
