The aliens landed on February 4, and they landed on Reddit. Their vehicle: a four-panel comic strip. "Friends arriving soon," one large-eyed extraterrestrial said to another, checking their watch. "Let us store irregular shapes inside shapes with flat surfaces."

"Your home is beautiful," two other aliens coo, appearing in the doorway.

"Thank you," responds the first pair. "We own things but have hidden them."

That was it. A simple strip that reframed a banal human tradition—cleaning the house in anticipation of guests, something countless people had done for the Super Bowl the day before—through the eyes of an interstellar anthropologist. Yet, Reddit welcomed its alien overlords with open arms: The strip, posted to the popular subreddit r/funny, received more than 30,000 upvotes.

For illustrator Nathan W. Pyle, who has published two books and built a significant social-media presence, it was a necessary first step for his newest creation. "When you build a big following, you can get thousands of likes on something even if it's not very good," he says. "Reddit has been crucial for me because they upvote and downvote things pretty objectively."

Three weeks later, those aliens have reappeared 11 times, and Strange Planet, as Pyle's burgeoning webcomic is known, has exploded online. "If it's something that makes Reddit laugh and it makes my mom laugh," Pyle says, "that overlap is a pretty strong indicator.” A dedicated Instagram account has more than 250,000 followers, and each new Reddit post outperforms the last. Birthday parties and wine tastings, sports fandom and coffee; by now, you've either sent one to a friend or been sent one by a different friend. The aliens, it appears, have found themselves a foothold on the internet.

Yet, the success of Strange Planet is only the latest in a recent resurgence of a very particular kind of webcomic. Four-panel strips have been a fixture since early 20th-century newspaper comics like Mutt and Jeff and the concomitant appearance of yonkoma ("four-cell") manga in Japan. It's the perfect three-act-structure: You start at one end, develop conflict in the middle two panels, and resolve with a punch line at the end. But thanks to a number of factors—not least of which is the rise of Instagram and Reddit—a gridded, two-by-two variant has come to dominate the internet.

First, though, you can probably blame/credit the death of Google Reader. "People don't go to websites anymore," says Gary Tyrrell, who has run the webcomics blog Fleen.com since 2005. Without the ability to push their work into your RSS feed, shareability became key for artists who needed to get their work in front of as many eyeballs as possible. The two-by-two, Tyrrell says, "knocks down one of the precursors toward virality: you've got something in a distinct chunk. Something about the two-by-two says you don't need to know what the previous was and what the next one did."