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?!
Due to the writers's different interpretations of what Kara Zor-El is/should be, Supergirl's runs/books/series tend to go from depressing and angsty to optimistic and light-hearted before switching back to dark again.
Supergirl (2005): Joe Kelly's run, where Kara was depicted as an angsty, perpetually depressed adolescent who believes is being coerced into murdering someone was followed by Sterling Gates' run, where she was a maturing woman who was finding her place in the world, feeling pretty happy with her life at the end.
Supergirl: Cosmic Adventures in the 8th Grade was also considerably wackier, funnier and light-hearted than the then-ongoing book, featuring crazy Silver Age-esque antics instead of Supergirl getting depressed.
In Wednesday Comics, the Supergirl story is more humorous, heartwarming, and less intense than the others. The story follows Supergirl as she tries to figure out why Krypto and Streaky are going berserk. The Super Pets' antics cause a lot of destruction, but it's played for laughs, and nobody gets seriously hurt or killed. Also, as it turns out, the story's "villains" have totally benign intentions, and Supergirl is ultimately able to communicate with them and resolve the conflict peacefully.
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.
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 (especially The Joker weren't allowed to kill people), the violence was toned down, and very silly and outlandish things happened on a regular basis.
Jason Todd aka Red Hood has undergone this in recent years. When he first made his debut/resurrection in Batman: Under the Hood he was an Ax-CrazyFallen Hero who would go much further than Pay Evil unto Evil, by being a pimp and a drug lord who killed cops and civilians who got in his way and even tried to kill Tim Drake. By the time of The New 52, Jason is a lot calmer and nicer and has less violent interactions with the Bat-Family, who have come to accept him despite his violent tendencies. By the time of DC Rebirth Jason has mellowed out so much he actually spares villains like Black Mask out of loyalty to Bruce.
