Post-it notes. The world would be in chaos without them. Nobody would remember anything. Nobody would be able to turn their office walls into superhero murals. Nobody would be able to leave passive-aggressive messages on the doors of communal refrigerators or plan their next funny prank. And nobody would be able to have the sort of epic sticky note battle that recently took place in New York.

It all started innocently enough. An employee at Harrison and Star wrote a simple “hi” in Post-it notes on her window and waited for somebody to respond. And somebody did. They wrote “sup”. So far, so civil. But this office prank didn’t stop there. Oh no. It was only just getting started! Both buildings host a number of marketing and media agencies and their inhabitants couldn’t resist getting involved in the action with their creative ideas. Soon enough the windows were full of funny messages and pictures with hundreds of Post-it note pads used. But as you’ll discover below, even the best pranks come to devastating end in the most unexpected of ways…(h/t: twisted sifter)

Update: Wonder what they did with all of those used Post-it notes? They were used as part of a fundraising campaign for the NY Veteran’s Hospital! Click here to learn more.

Everything started with an innocent “HI” on the 6th floor at 75 Varick Street in NYC

Image credits: @freshasthedayshewasborn

Soon, “Sup” appeared on a building from across the street at 200 Hudson

Image credits: @Vinvox

As both buildings had a lot of media and marketing agencies, it eventually turned into WAR

Image credits: u/craftBK

The windows started filling up with funny pictures and messages

Image credits: Mike Segar

Somebody made a Snapchat icon

Image credits: Mike Segar

Others took a more random approach

Image credits: @gloddy

Even the Angry Birds got involved!

Image credits: Mike Segar

Post-it manufacturer 3M also joined the war by providing free ammunition (i.e Post-it notes!)

Image credits: Mike Segar

As the war got more creative, it seemed that nobody would win

Image credits: @kBostley

Not even Spiderman could stop it!

Image credits: Mike Segar

With no other option, Havas Worldwide brought the war to an end with this epic mic drop

Workers stayed late with beer and pizza to create the spectacular finale, and fellas from Spectacle Studio later posted this video

Image credits: spectacle_studio

Unfortunately, the battle was ended by building managers who ordered all participants to have everything taken down by the weekend.