Five years, ago, Mendl Weinstock made a promise to his sister Riva.

“My sister was talking about her wedding as if it were tomorrow, when she wasn’t even dating anyone at the time,” he told Insider. “Just to make her mad and get a reaction, I told her if she makes me come to the wedding, I am bringing a llama with me. After a few minutes of arguing, she tried to use reverse psychology on me and said, ‘OK, the llama is invited to the wedding.’”

In true little brother fashion, Mendl made sure she never forgot about the invitation.

“He has been torturing me with this, in good fun, and has been reminding me of this probably twice a week for the last five years,” Riva said. “I have tried striking so many deals, I have tried doing literally everything possible to make sure it didn’t happen, and lo and behold, there was a llama at my wedding.”

When Riva got engaged in October, Mendl put his plan into action.

“When he sets his mind to something, he makes it happen,” she said. “Literally, I called him to tell him I was engaged and his response was, ‘Great, I’m calling the llama farm now.’ Probably not even an hour later, I got a text that said his llama rental was confirmed.”

Indeed, when Riva got married in Cleveland, Ohio, on Sunday, Shocky the llama joined the festivities. Mendl even commissioned a custom llama-sized tuxedo for the big day.

Siblings Riva and Mendl Weinstock with the llama.

Since Riva knew to expect the gag, she bargained with her brother to make it as unobtrusive as possible.

“I promised him that I would take one picture,” she said. “I said, ‘I will not stand next to the llama, I will not touch the llama, but I will take one picture.’ My friends can attest that I went outside, I took exactly one picture, and then I went right back inside and was not having any more of it.”

One photo was all it took. Mendl posted the picture on Reddit, where it has received over 154,000 upvotes and counting.

Riva had no idea that an inside joke with her brother would go this viral – especially since there’s precedent for bringing llamas in formalwear to weddings. There’s even a whole Instagram account called @weddingllamas devoted to the subject. But she thinks their playful sibling rivalry and her unamused glare made enough people laugh to kickstart the photo’s internet fame.

“I think it’s my facial expression, because I really don’t look particularly thrilled with the situation, but I think that’s what got people’s attention,” she said. “That was my face from the moment I walked outside, and it was completely intentional. That’s pretty much my face constantly when I look at my brother.”

The joke continued inside the wedding hall, where friends placed inflatable llamas on their chairs at the sweetheart table.

The llama theme continued in the banquet hall.

The actual, live llama stayed at the wedding for around half an hour, posing for pictures with guests, before returning to its farm about an hour outside Cleveland. Riva is already planning to make Mendl pay for his prank.