On November 20, 2004. Yale students posed as a Harvard pep squad and distributed posters to the Harvard fans, telling them it would spell out "Go Harvard", while in reality a different message would be displayed.
Although the final result wasn't as clear as it could have been (you can barely make it out if you squint just so), I'll give the Yalies credit for attempting to pull off something like this.
Interestingly, if you see the picture in print anywhere, it's much clearer, obviously photoshopped!

That's the greatest thing ever. Period.

Awesome Arr...

Ha! Great post.

*dead

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