In a noisy and bustling stretch of Lower Manhattan, where cabdrivers blare their horns and pedestrians scurry by with laser focus, people have places to be, it seems, and are disinclined to waste any time getting there.
But every so often, someone walking along Canal Street glances upward and pauses. And then pulls out a phone to take a picture.
On Tuesday, the windows of the office buildings on both sides of the street, near the Holland Tunnel, were covered in sticky notes, recreating Marge and Maggie from “The Simpsons” and a Superman logo that stood as tall as an entire floor. There was a homage to Prince, his symbol depicted in purple Post-its. And there were cheekier messages and references to memes as well: “5pm yet?” and “Bye Felicia.”
The creations are the result of a friendly back and forth between the firms, mostly advertising and marketing companies, on opposite sides of Canal Street.
“Wow, that’s funny,” said Alexa Catania, 19, who stopped when a mosaic of a white ghost against a yellow background caught her eye; she thought she and her friend had stumbled across the offices of Snapchat on their way to lunch. “I was trying to figure out what it was.”
“Only in New York,” her friend Gerald J. Ruland said, as Ms. Catania snapped a picture.
The whole thing started last week, when “Hi” appeared in a window in the building at 75 Varick Street on the north side of Canal. Across the street, in the offices of the advertising company Havas Worldwide, at 200 Hudson Street, someone responded with “Sup.”
“That’s how simply things can start, with a little ‘Hi,’” said Toygar Bazarkaya, the chief creative officer for the Americas at Havas Worldwide.
It blossomed quickly from there, with workers sketching out designs and using scores and scores of the adhesive notes in a range of colors to create their displays, many of which have grown far more sophisticated than the initial text-message shorthand.
“It’s cool to see it evolve over six floors,” Jeremy Pagano, who works in account services for an ad company on the north-side building, said while taking a smoke break outside.
“It has really come to life,” his co-worker Angela Donza said.
The back and forth has generated lots of attention on social media, with hundreds of pictures posted on Twitter and Instagram, with hashtags like #CanalNotes and #PostItWar. Even the maker of Post-it notes caught wind of it and has sent the companies involved briefcases packed with a variety of notes in different colors.
Inside the offices, workers have found it exciting to watch everything unfold.
“It’s definitely surprising,” said Kristina Bostley, an editorial manager for Biolumina, a pharmaceutical advertising agency in the building on the north side. “We never really know what they’re planning, and they don’t know what we’re planning.”
It seems unclear where the competition is headed. It started organically, Mr. Bazarkaya said, and he hopes it continues that way. It has been a fun way for workers to have another outlet for their creativity — after work, during lunch or in the occasional lulls during the day, of course.
“We have a day job,” he said.