The 2/22/2017 4chan /x/ Alien Photo Incident:
On february 22 of 2017, around 12am or 2am, a thread was posted with the subject:
"24489 Taken Aprox 24 miles north west of Luke Airforce Base Phoenix Az. Lab H4C"
Allegedly featuring a high-res photograph of a reptilian humanoid.

The photo was seen by several witnesses, descriptions include:
“The aliens head was seen from the left side and it was looking to the left in the picture and slightly at the camera. Almost diagonally”

“They ayylmao looked like it had scales all over and was dark in colour. Its eyes looked like dried up prunes and had human like features but much smaller in comparison to its head.”

“I did see the alien, yellow scales black eyes with small pursed lips. Thought it was a shill thread so didn't open but saw the pic”

The thread was up for 45 seconds before several Cloudflare servers went down, resulting in the entire site crashing and going offline for several hours.

Subsequent threads inquiring about the picture were filled with spam, hundreds of fake images, attempts at derailing, and were often deleted within minutes of being posted.