Let me preface this by saying that I kept up with this years ago as it was happening, and, as such, I haven't been able to find a lot of the sources from back then, as many people have changed blogs or deleted altogether. If you were more involved and can source/correct some of this information, feel free, unless you were a tin-hatter, in which case I really, really question your sources. Different beard styles with names.
So: this drama combines two of the wildest kinds of fandoms- boy band superfans, and tin-hatters, who not only shipped two IRL people but believed they were secretly dating and forbidden from announcing it by some shadowy, evil management figure. The tin-hatting fandom around Louis Tomlinson and Harry Styles of One Direction (called "Larries") is one of the most, er, passionate I've ever seen. Top hits include sending NSFW art of Louis and Harry together to Louis's underage sister, believing Louis's girlfriend Eleanor was actually a set of triplets acting as his beard(s), and being invasive enough that Harry and Louis said Larries had affected their friendship.
2015 was a wild time for the One Direction fandom as a whole. First, Louis broke up with Eleanor, leading Larries to speculate that, with "Louis's beard(s)" gone, he and Harry would finally be allowed by Shadowy Evil Management to come out of the closet. Then, Zayn Malik left, the band went on hiatus, and in the middle of it all, shit really hit the fan when a woman named Briana announced she was pregnant with Louis's kid- a scandal referred to as Babygate by those who believe the whole thing is fake.
Obviously, Babygate didn't work well with the theory that Louis was secretly gay and in a long-term relationship with Harry. And while girlfriends could be written off as beards, and rebuttals from Louis and Harry as scripted by management, a baby was harder to so you'd think.
Larries spent the next few months in denial. The pregnancy wasn't real until management confirmed it, until Louis confirmed it, until he confirmed it in an interview instead of just on social media, etc- all of this happened. Then, Larries turned to picking apart Briana's body for signs that she was faking the pregnancy. One picture was taken that, because of the angle, made it hard to see her bump. They immediately took this as proof that she wore a fake bump, and had somehow forgotten it in a picture posted publicly on Instagram. This continued after the baby was born, when everyone became experts on what a woman's body should and shouldn't look like after birth. They ignored any photos that went against their belief and spread the ones that made her look "too thin to have just given birth" like wildfire. This was a common pattern with Larries- with Louis and Eleanor and any other girlfriends, they'd ignore pictures where the couple looked happy, and spread the ones taken at unflattering angles as proof the couple was actually fake and miserable.
Finally, Louis's baby was born- a boy, named Freddie. This led to even more denial. "It's not real because they haven't posted any pictures!" A few black-and-white photos surfaced. "Well, the pictures aren't in color, so they're photoshopped!" Color photos were posted on social media. "Well it's not a video, so it's not proof!" Paparazzi stalking Louis and Briana got a video of Freddie crying. "Well, it's still not a good video, he could just be a doll!" Louis posted a video of Freddie kicking a toy. It was pretty obvious to everyone with eyes that this baby was real, and that Louis was helping take care of him and happy to have him around.
This still wasn't enough, however. Some Larries remained on the hyperrealistic baby doll theory, claiming that Freddie's movement in videos was unnatural and obviously doll-like. This theory became harder and harder to believe as more content of Freddie was posted, so most switched to a new one- that Shadowy Evil Management had hired Briana as a beard, faked her pregnancy, paid off another couple to use their real baby in social media posts and paparazzi shots, all while also employing Louis's then-girlfriend Danielle as yet another, simultaneous beard.
Goatee beard styles
(You'd think management could've saved money by hiring an already-pregnant woman in Briana's place, using her baby, and having Louis pretend to date her. It'd be a one-stop-shop instead of an entire operation involving a fake mother, two real parents, a fake baby, and a fake girlfriend.)
Denial continued, along with a lot of anger directed at Briana and whoever they believed Shadowy Evil Management was at the time (it's important to note that Louis went through some management changes around then after leaving 1D, so Shadowy Evil Management had to change identities). Nothing Briana or Louis did was ever enough. If they posted pictures, they were obviously rubbing it in everyone's faces and desperate to prove Freddie was real, so Freddie had to be fake. If they didn't post pictures, then it was obviously fake because parents love to post pictures of their kids online. If Louis talked about Freddie in an interview, he was obviously faking enthusiasm and trying to hide how miserable he was, and why couldn't the media just focus on his music? If he didn't talk about Freddie, then it was obviously fake because why wouldn't he talk about his kid?
On top of this, they criticized every one of Briana's parenting decisions (that they could infer from her social media posts) and accused her of neglect, which seems completely unnecessary if Freddie was just someone else's baby hired out for a few photos and videos every now and then. They hate-stalked her social media, and she was called a lot of names that rhyme with "bold-bigging bore" (despite her apparently just being an employee of Shadowy Evil Management, not the actual mastermind behind it).
There's so much more down this rabbit hole that I've only scratched the surface.
One fan got Louis's personal phone number, called him, and told him she hoped Freddie died.
Another fan bought a hyperrealistic baby doll and made her own Instagram account where she imitated all of Louis and Briana's pictures with her doll, to...prove they were fake? Make fun of the baby?
The same fan bought a bunch of URLs related to Briana's family and started websites trying to prove Freddie was fake, after submitting her "proof" to several tabloids and being ignored. Briana's family ended up suing her (the websites were incredibly antagonistic towards Briana).
Yet another fan drove several hours to the county where Freddie was born to see if a birth certificate actually existed for him. Surprise surprise, it did.
A well-known Larry who made popular "proof" compilations had a username related to Freddie Mercury. Some decided Louis had deliberately named Freddie as an acknowledgment of that Larry, and a hint that Freddie wasn't actually his son. This in spite of the fact that apparently Shadowy Evil Management had so much control over him that they could force him to act like a father to a fake baby.
At one point (I can't remember if it was before this or during), it came out that many of the most popular Larries were part of a group chat, and, whenever Louis or Harry got pap'd doing something that went against their theory, the popular Larries all worked together to fill everyone's newsfeed with very pro-Larry stuff as a distraction, so no one would see the paparazzi photos.
There were also constant predictions that "all the clues point to #Babygate ending on x date!" that would immediately be forgotten when nothing happened on x date. For a big list of these predictions, check out failedlarrypredictions which started back in 2015 to remind people how many predictions had failed, and is still going because there are still people out there making predictions.
Freddie, in case you're wondering, is now about three and a half, and Louis still claims to be his father and has still not come out as gay or secretly dating Harry Styles. The Larry fandom has dwindled, but they're still around, or else have moved onto other tin-hatting fandoms.
Top beard style 2016
I really wish I could find sources for more of these incidents because I recognize that some of them are fairly unbelievable. If you want to go further down the Larry rabbit hole, though, I recommend you check out this post - it's a master post of debunks of Larry "clues". A lot of the links are broken as blogs have moved or deleted, but it's still a good collection of Larry theories up until about the birth of Freddie, and why those beliefs were all, in fact, bullshit.
TL;DR: Confirmation bias & willful ignorance are stretched to their limits by an infant.
(And if you still genuinely believe in Larry in 2019...I'm not interested in a debate, the debunks are out there, and Freddie isn't going anywhere).