In Prime Baby, the sluglike aliens turn out to be "missionaries of smiles and happy feelings". They hold sing-alongs and knit socks for the homeless.
Superman is a rare Lawful Good example of this trope, at least with regards to his treasured home city of Metropolis. For the rest of the world, he usually takes a more low-profile For Great Justice route.
It would be more accurate to say that Superman maintains a balance between For Great Justice and For Happiness, for the most part. Over the years, Superman's motivations to do good have changed. In some stories, he wants people to be happy. In others, he wants to bring evildoers to justice. It's all Depending on the Writer.
In the Star Wars Expanded Universe, the Zeltron hat is this...mostly. Justified as they're a race of empaths. If someone's unhappy, the whole block knows it and can feel it. The sociopaths of their species usually travel off-world to get away from the good cheer.
Le Fabuleux Destin d'Amélie Poulain, who decides her destiny is to bring happiness and beauty to the lives of others - though she's not above cheating, fabricating, or deceiving to do so.
In Happy-Go-Lucky, Poppy just wants to share the joy and that everyone is happy. That goes so far as trying to cheer up even the grumpiest of people she meets.
Giselle in Enchanted pretty much acts on this as her life philosophy, up to and including impromptu (delightful) musical numbers.
Johnny Appleseed was famous for this. Though he spent most of his life a simple hermit, he made it his mission to cover the United States territories with apple trees so that everyone could enjoy their flowers and fruit. That and get drunk. Apple cider (what he was best remembered for giving to people) ferments very quickly.
Kushiel's Mercy has Ptolmey Solon, the world's probably smartest man, who holds that happiness is the highest form of wisdom.
Vianne from the novel Chocolat doesn't believe in God or sin or forgiveness. She believes that "The only important thing is to be happy" - and does her best to make it happen with amazing gourmet chocolates. Sounds like a solid strategy to me!
Wicked Lovely has the Summer court, who are described as 'happy by nature' and 'frivoulous and passoionate'. They oftentimes tell others to 'choose happiness'. However, due to their nature as part of The Fair Folk, they often put happiness before things like morality and loyalty, on one occaision telling Seth to leave Aislinn because he'll be happier that way.
"Sometimes it's not about being happy, but courting happiness." -Siobahn.
In Animorphs, the Pemalites fit this trope to a T. Created by The Ellimist to spread life, love and freedom, they did exactly that... until Crayak's pet creation, the Howlers, straight-up slaughtered their asses. It's worth noting that the Howlers are also like this, Crayak just gave them a warped sense of what people find fun.
In Kamen Rider Double, Shotaro Hidari makes it his mission to make sure no one in Futo cries. The fastest way to set him off is to make sombody cry in his presence.
Gentaro Kisaragi, aka Kamen Rider Fourze, also strives to protect the smiles of his friends. And his goal is to befriend everyone he meets.
In the Doctor Who serial The War Machines, the bartender asks Polly to help cheer up Ben. Polly comments on how reliably she is called on for such measures.
In the Dungeons & Dragons setting Scarred Lands, the titan Gulaben held the powers of granting happiness. The mortal peoples believed her to be For Happiness, and her popularity made her a threat to the Gods' reign over the world. Claiming that her power was merely a sinister kind of Getting Smilies Painted on Your Soul, the Gods captured her and destroyed all memories of her so that no one would try to set her free. The official truth is that she was a fickle and cruel titan, who might kill you even as she induces pleasure beyond imagination. The gods simply did what they had to do. And since we no longer remember the real truth about Gulaben, we'll just have to take their word for it.
This is pretty much Felicia's outlook on life — pursue happiness, and try to make as many other people happy as possible along the way.
Aang told Iroh how he'd been told to let go of his love for Katara in order to use his full power, and had refused to do so. Iroh immediately tells him he did the right thing, and that "Power and perfection are overrated".
Aang himself has something of this, as even though he does understand it is his destiny to beat the Fire Lord and restore balance to the world, he frequently puts that mission on hold in order to let himself and others have fun.
Princess Celestia seems this way, acting like a light-hearted pony who doesn't take herself too seriously and even enjoys a good laugh at her own expense. Over time, we've seen her get more serious, until it's apparent that keeping everyone safe is her main concern, and having fun is what she does in her rare moments of leisure.
This ethical position is an important form of utilitarian philosophy, and has been consistently popular among moral philosophers since the Enlightenment. Jeremy Bentham and John Stuart Mill were both major developers of the theory, although "happiness" may sometimes be replaced with a more generally defined "good" or "well-being", or something else altogether like "freedom" or "beauty".
Note that there are multiple types of utilitarianism. For instance, while Bentham indicated that one should always do what increases happiness in a sort of general kind of way, Mill's definition is rather more complex; most notably, he said that one should always follow the rule that, if consistently applied by everyone, would lead to maximum happiness/the greater good.
The United States' Declaration of Independence includes "the pursuit of Happiness" as one of man's inalienable rights.
The King of Bhutan measures the prosperity and success of his nation (and, hence, his rule) in terms of Gross Domestic Happiness. While one of the world's poorest countries when measured in dollars, there are more important things in life than luxuries and the Bhutanese people are considered among the most happy ones with the life they have.
The people who give out "Free Hugs" on the street.
Random acts of kindness.
The Wiccan Rede translates to "If it harms none, do what you will." Of course, that means stopping to think about the potential harm of one's actions before undertaking something and taking the route that will cause the least harm and the most happiness when harm cannot be prevented.
LaVeyan Satanism advocates doing whatever makes one happy, as long as it does not infringe upon the rights of others.
This is really the soul of entertainment. Given, a large portion of it is made for monetary purposes, but the first person to transcribe a story couldn't have done it out of greed, and still those writing for money are outnumbered greatly by those who just hope for somebody to enjoy their tale. And even with the monetary slant, much of that ends up being cost of living. When it comes down to it, any entertainment/creative industry from music to video games has such high levels of risk/reward and employment that if you really wanted to be rich, you're better off being something like a doctor or lawyer.
Article 4 of the French "Declaration of the Rights of Man and Citizen": Liberty consists in the freedom to do everything which injures no one else; hence the exercise of the natural rights of each man has no limits except those which assure to the other members of the society the enjoyment of the same rights. These limits can only be determined by law.