These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
These books are often placed in the children's section in the library, and Nick Jr used to air the Tintin cartoons (which were clearly intended for children). Granted; this is a very mild example seeing as the books are probably "PG" rated at most, a rarity given their original target audience. However, this is a bit more of an instance where it's not "Too violent", "too gory", or "Too sexy" for children, as it is "Too complex" for children. Several of the books (Namely the first few and the last one) are actually political satire, something most kids actually wouldn't really understand. However, children could still enjoy many of them for the adventures, later (mis)interpreting the political satire and history nods as a Parental Bonus.
Badass Decay: General Alcazar could fit in this category. He seems pretty badass until you learn who wears the brightly colored pants in his marriage.
Broken Base: Is The Castafiore Emerald an entertaining diversion, a deliberately silly chamber piece that trades in the high stakes and tension of the rest of the series for humor and character work? Or is it a pointless exercise in wheel-spinning, a waste of the heroes' and the readers' time? You can find both views expressed very eloquently here and here.
Bizarro Episode: Flight 714. With the most explicitly supernatural third act since The Shooting Star, an unprecedented comic bent to the villains, and a healthy dose of Laser-Guided Amnesia for all involved at the story's resolution, this is often considered the strangest story in the series. It's been ventured that this is meant to be more an Affectionate Parody on Hergé's own part than a tale to be taken completely seriously.
Fanon Discontinuity: The first book, Land of the Soviets, usually isn't counted as part of the series continuity by most fans. Tintin in the Congo is also not acknowledged by some, owing to the rather embarrassing elements of its storyline - although others grudgingly accept it as canon due to the fact that Tintin in America is actually a direct follow-up to the events of Tintin in the Congo.
Fashion-Victim Villain: Rastapopoulos in Flight 714 is dressed in fancy pink-shirted cowboy garb. Hergé himself said that he wanted to ridicule him and make him a "luxury cowboy" (sic).
Freud Was Right: Any scholarly or academic analysis of the series draws heavily on Freud and psychoanalysis in general...and will claim that just about everything is a sexual metaphor.
"Funny Aneurysm" Moment: Most of Tintin in the Land of the Soviets are laughably crude anti-communist propaganda, with Soviet agents planning to blow up all the capitals of Europe and red soldiers trying to drown Snowy For the Evulz. Some scenes of the oppression in Stalinist Russia, however, rings painfully true, for instance when Tintin helps a kulak hide his grain from the bolscheviks. It has been estimated that half a million kulaks were killed and 1.8 million people starved to death due to forced collectivization and confiscations of grain in the early thirties.
While under the influence of truth serum, jerkass billionaire Carreidas in Flight 714 goes on at tedious length about his first evil act - stealing a pear as a child. Stealing pears was also St. Augustine's (354-430) first step on the path of sin, according to his famous Confessions.
Growing the Beard: After the first two books, the series picked up in terms of story quality. Cigars of the Pharaoh was the first story that attempted to be a cohesive storyline rather than just being a loose collection of set pieces based around a particular country, although Hergé himself considered the following story, The Blue Lotus to be the point where the stories really started to get good.
Tintin's hunting of an elephant and a rhinoceros in the original, black-and-white version of Tintin in the Congo, not least because of how the populations of both animals have dwindled in the years since the release of that version.
The plane hijacking in Flight 714 and the real life hijacking of Flight 370 are so similar it's speculated the latter was inspired by the former.
The references to "coke" in The Red Sea Sharks. At the time it was widely used to refer to as a derivative of coal, but nowadays "coke" usually refers to either Coca-Cola or cocaine. The latter interpretation makes Haddock's shocked reaction to Tintin's question if their ship is carrying any coke look particularly hilarious.
In The Castafiore Emerald, Bianca Castafiore gives Haddock a violent and ill-tempered pet parrot named Iago.
Also in The Castafiore Emerald, Captain Haddock, a character with black scruffy hair and beard, falling down the stairs...
In The Blue Lotus the Japanese are depicted as being an oppressive and militaristic force of evil, while the Chinese are portrayed in a generally very positive and wholesome manner. Nowadays, most writers would likely have the two swapped around.
Ho Yay: Tintin and the Captain, and less obviously, Tintin and Chang from The Blue Lotus and Tintin in Tibet.
Inferred Holocaust: Happens at the start of the first Tintin story, Land of the Soviets, as the train that Tintin is taking to the USSR gets blown up by a bomb, and all the passengers and crew are apparently killed (except for Tintin and Snowy, who survive... just because, really).
Internet Backdraft: Has your heater conked out on a winter day? Praise or denounce Tintin in the Congo.
It Was His Sled: Everybody knows that Roberto Rastapopoulos is little more than a movie director...
Not So Crazy Anymore: In "Destination Moon", Captain Haddock spends a lot of time mocking Professor Calculus for saying that travel to the moon is possible. When the book was published, in 1953, this was understandable, but after 1969, HADDOCK seems like the crazy one...
"Caramba! Encore raté!" from Broken Ear, whenever a plan fails or a target is missed.
The catchphrase "Je dirais même plus..." (To be precise...).
The Scrappy: Jolyon Wagg is considered annoying by both the in-universe characters and the readers.
Seinfeld Is Unfunny: Young readers who have seen many adventure comics/cartoons find Tintin to be cliché.
Shipping: In the draft of Alph-Art that Hergé left incomplete upon his death, Tintin investigates the murder of an art expert and initially accuses the victim's assistant, Martine Vandezande, of being in league with the killers. In Yves Rodier's unauthorized ending, Martine invites Tintin to meet her parents over dinner. Fortunately for the sanity of Tintin fans everywhere, Rodier didn't show whether Tintin accepted or rejected the invitation.
Usually trying to be averted, but if there is some, it is there BIG TIME. For instance, Tintin in the Congo. Where he does everything dissonant known to 21st century man: Blowing up a rhino by drilling dynamite holes into it, shooting an ape to use his skin as camouflage, all the way down to teaching native children imperialist Belgian ideology. Fabulous, eh?
Note that The Blue Lotus came out during the Japanese invasion and occupation of China. As such, that unflattering depiction is a scathing indictment of Japanese imperialism of the times and no different from similar depictions of Nazi Germany. For comparison, in the The Crab with the Golden Claws, there is a sympathetic Japanese character, who appears in the very beginning and the very end, who is not caricatured and is not a Jerk Ass of any sort.
Or in The Shooting Star (published during WWII, when Belgium was occupied by Germany), where Tintin's expedition's nemesis is a certain Americanindustrialist called Blumenstein. In the later versions, the country was renamed Sao Rico and Blumenstein was renamed Bohlwinkel (which actually doesn't make it any better).
Or (apparently) Tintin landing in the British Mandate of Palestine in Land of Black Gold, as it was replaced with a Qurac-esque nation in later editions.
Or when the world was allegedly going to end, and two stereotypical Jews are seen talking about it, one of them saying that would spare him paying a debt to another Jew.
Villain Decay: Rastapopoulos to a tee. In his earlier appearances, he is a powerful, deceptive and menacing chessmaster. Flight 714 sees him reduced to a pathetically short-tempered pink cowboy who can't think even one step ahead (he's still pretty evil though, as he is quick to tell us). His dragon Allan falls prey to this too, becoming nothing more than a dumb and cowardly henchman. Note that this was done on purpose; Hergé deliberately decided to ridicule his villains at this point.
Badass Decay: Emir Ben Kalish Ezab suffered from this in the Nelvana series. The comic version of the Emir did sometimes get emotional about things regarding his son, but was otherwise a guy who you definitely wouldn't want to mess with. The animated version on the other hand was such a simpering crybaby that it was frankly amazing that Bab El Ehr hadn't managed to overthrow him already.