What's great about this sort of humor is the way that it makes individuals feel less alone. Parenting is isolating, and it's easy to assume you're the only one attempting to navigate meltdowns at the supermarket shelf or a child who won't remove pajamas to attend school. But when you turn those experiences into humor that's being shared by thousands of others, it puts the struggle back into context. Rather than being just stressful, it's something to joke about, something you can laugh with other people who've been through it too.
Finally, parenting tweets and memes succeed because they take individual chaos and render it in terms everyone can understand. They show that humor is a survival strategy, that the worst parts of raising children are also the most human, and that there's comfort in knowing other humans are waging the same battles. A successful parenting meme doesn't mock you, it lets you know you belong to a bigger, sicker, funnier community.
