From graffiti campaigns to tea blends, the fans of BBC’s Sherlock have proven they know how to keep the love going strong even in between seasons. And if the party gets a little racy? No one’s complaining—least of all the hundreds of fans enjoying Red Pants Monday! (Link NSFW.)

The popular series starring Benedict Cumberbatch and Martin Freeman is known for its huge slash fandom. The duo have captured the hearts of millions of fans, and accordingly, Sherlock/Watson slash proliferates in fannish corners of the Internet.

A recent fan art trend involves putting Watson in bright red briefs. The image is so popular it’s become a weekly festival of fan art, fic, and even cosplay known as Red Pants Monday.

Reapersun, a well-known Sherlock fandom artist, created the first instance of Watson in red pants just under a year ago (NSFW). The image was immediately popular, but it took a while for it to turn into a fandom-wide trend. When Reaper, along with her friend Sexlock, combined forces to create an art roleplay journal known as reapersex, they started by reintroducing the now-infamous red pants, and soon enough, a meme was born.

Lockedin221B was the first person to take the trend and ask, “can we just make Red Pants Monday a thing?” The trend was so popular that it led her to create an entire Tumblr devoted to celebrating fandoms’ days of the week, a concept honoring pre-existing pan-fandom trends (like Penis Friday) as well as new ones.

Though all of this intense love for “Johnlock” might seem new, Sherlock Holmes has long been a prime target for queer subtext: In 1941, Rex Stout, author of the popular Nero Wolfe detective series, famously proposed that Watson was a woman, and director Billy Wilder fully intended that his 1970 comedy The Private Life of Sherlock Holmes be a representation of the world’s first canonically gay consulting detective.

But fans seeking insight into the Sherlock/Watson dynamic might want to try a different tag. Reapersun, the original creator, confessed to the Daily Dot that she feels the red briefs that started it all are “out of character because John seems like a more practical guy... But then he does wear those occasionally whimsical sweaters so who's to say? I think they're a bit juvenile for him, at the very least, and something about a dude wearing underpants that are slightly too young for him is kinda cute.” Indeed, age hasn’t stopped fans from having fun objectifying Watson, played by the 40-year-old Freeman.

Stout and Wilder undoubtedly never imagined anything like the Sherlock fandom when they first posed questions about the relationship between Sherlock and Dr. Watson. But to be fair, no one anticipated the role Tumblr would play in proliferating an apparently infinite variety of fandom expression.

“I don't think it would've worked as a meme on any other site,” Reapersun told the Dot. “Tumblr's just set up to create and share related content like this so easily.” Fans have certainly been generous: In the two months since its creation, the trend has been going strong, featuring minimalist posters, serious portraits, and even a special flavor of Sherlock tea.

“We're going to get to that point when people forget about the Monday thing,” Reapersun predicted, “but at least there are lots of people going down with the weird underpants fetish boat with me.”

And why exactly is that boat red, again?

Turns out there’s no mystery: It’s simply her favorite color to paint with.

Image by mystradedoodles/Tumblr