"Don't be ridiculous. We would never shoot the Hulk into space!"
What's ironic is that the Mini Marvels comic strips included at the end of the mainstream Marvel universe actually parodies the shallowness and silliness. The Mini Marvels strips point out how the stories taken seriously are much more ridiculous than their Lighter and Softer counterpart.
The original 1980s version of Power Pack, while not nearly as angsty as Marvel's other works, took itself seriously and attempted to be a serious, but not as serious as usual, comic about kid heroes, with a fair amount of characterization, intelligent plots, and good quality storytelling. It actually tries to realistically portray what children who find themselves with superpowers might actually go through, but still falls short of stereotypical comic angst. The 2000s remake is aimed squarely at a quite young audience and has much cuter art and simpler storytelling.
Tiny Titans is an even lighter version of Teen Titans compared to the TV show. It takes places in a bright happy world where some of the worst things the elementary school Titans need to worry about are: embarrassingly loving father Trigon, grumpy lunch lady Darkseid, and stern principal Slade. In both versions of Teen Titans, Trigon is a demon who wishes to conquer Earth and turn it into hell, Darkseid is out to conquer all life, and Slade is an amoral mercenary and assassin. To say nothing of the comic version Starfire's character design...
The 1994 Continuity Reboot of Legion of Super-Heroes. Over the previous decade, the comic had been hemorrhaging readers for years, having gone from happy young superheroes in a bright and shiny future to cynical adults struggling to hold society together (and the insanely complex Continuity Snarl that came about after Crisis on Infinite Earths). So, the comic started over at the beginning with a focus on youth and idealism. (It got Darker and Edgier again when Dan Abnett and Andy Lanning took over writing duties years later, but that's another story.)
Done in-universe in The Sandman: Abel tells the baby Daniel the story of how he and Cain came to live in Dream's dominion... well, a version appropriate for a toddler, anyway. The story involves Super-Deformed versions of themselves, Dream and Death. Cain is utterly sickened. It's hilarious.
Cain: What kind of sanitized pablum are you feeding the child?!
Superman was originally a much rougher and reckless tough guy who was eager to terrorize his enemies and even kill his enemies when suitable. There was even a story where Superman sought to encourage urban renewal by going on a rampage smashing up slums. Within a few years, Superman was changed into his more familiar big boy scout personality.
Transformers: Wings of Honor: The Text stories are usually more humor based, compared to the comicstrip which ended with most of the characters dead. The Generation 2: Redux stories are a lot more upbeat and funny and, on the whole, more optimistic, with the next generation seeing a future working together, rather than an inevitable war that the Wings comics lead into.
Discussed in Spider-Verse when Morlun drops in on the Spider-Man and His Amazing Friends universe. He notes that the universe is much lighter than the other ones he's been to. So light that that universe's Spider-Man cannot describe the fact that Morlun just massacred the Spider-Friends and he's next.
The comic became this when Ian Flynn took over on issue 160. Though there were still some darker arcs, the tone was generally lighter and more comical than the last 100 or so issues, which were mostly dark melodrama filled with tragic moments and little to no comic relief.
The Warrior Catsgraphic novels (aside from The Rise of Scourge), compared to the main series: they tend to have more comedic parts, the plot is usually less fighting-focused, and violence is usually bloodless and sometimes even accompanied by goofy sound effects. They focus more on characterization than the Family-Unfriendly Violence heavy books do. Most of the artists also draw the characters in cartoony or animesque styles, which help alleviate some of the darkness of the series (in contrast, book artwork features realistic cat designs).
Batman underwent this in the 1950's and 60's as a result of the Comics Code being put in place, he wasn't the dark brooding figure as we know him today, his villains weren't allowed to kill people, the violence was toned down, and very silly and outlandish things happened on a regular basis.