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.
Crazy Awesome: Some of Gaston's inventions, like the propeller on the roof of his car that recharges the battery: it starts lifting the roof off, so Prunelle grabs, then the whole roof lifts off and Prunelle is sent on a long flight, ending because of a stupidly-placed wall.
Growing the Beard: Many people found the comics more funny after Franquin created other recurring characters and that the plot doesn't only focus on Gaston and Fantasio.
Hilarious in Hindsight: The Other Wiki mention that there's a real-life businessman named De Mesmaeker in Belgium. Needless to say, taking him seriously whenever he has to sign contracts isn't easy.
De Mesmaeker was actually inspired by one of the relatives of Franquin's coworkers, who coincidentally was a businessman. The man took it rather well, to the point of jokingly asking "Where are the contracts ?" while dealing with French clients.
Ho Yay: Just a bit. In one comic, it is revealed that Gaston likes Fantasio even better than sleeping. Another features a gag which, in a way, sets them up as a couple — Gaston swallows the prize inside a box of candy and has to go to the hospital. When the prize is retrieved, a nurse cheerily tells Fantasio, who is waiting worriedly in the hallway, "It's an airplane!"
Strawman Has a Point: One strip has Prunelle chewing out Gaston for napping with the cat sleeping on his lap while the others are working. He gets to work, retorting that if every dictator, general etc. would do just that once in a while, he'd feel a lot better. Prunelle's thoughts: "What do you reply to a guy who's right?"
What an Idiot: Gaston comes up with a simple system to pollute less: fitting a giant balloon to his ar's tailpipe, ensuring that the toxic fumes don't escape into the atmosphere. And then, of course, he removes it at the end, requiring gas-mask equipped rescuers to intervene to reanimate all the suffocated bystanders.