A NASA astronaut once surprised his crewmates by wearing a gorilla suit aboard the International Space Station.
Judgement: 
Former astronaut twin brothers Mark and Scott Kelly arranged a gorilla suit stunt aboard the International Space Station that the crew members knew about in advance. But it was Scott, not Mark, who was recorded carrying him into space, contrary to some social reports.
That's what former NASA astronaut Mark Kelly claims 'once' on board the International Space Station" ( smuggled in a full gorilla suit archive) and "haven't told anyone about it". (archive) on social media (archive) since at least 2016. Take for example the below post on Reddit:
Interestingly enough, Mark Kelly has a twin brother - also an astronaut - named Scott, and we've come across many social media posts, like the one below, that made the exact same claim about him:
In 2016, former NASA astronaut Scott Kelly smuggled a full gorilla suit aboard the International Space Station but didn't tell anyone about it. Until one day he decided to sneak up on his fellow crew member pic.twitter.com/uop15g6bHW
- WTF Facts (@mrwtffacts) February 17, 2023
While this stunt did indeed happen, reports like the one above have confused some details about the #SpaceGorilla incident. Mark and Scott Kelly planned the gorilla suit stunt together, and the rest of the International Space Station (ISS) crew was told about it in advance. Mark, who was not on the ISS at the time, arranged for the suit to be sent from Earth to Scott, and Scott was the one actually wearing the suit in the video.
The story continues
Both Kelly brothers posted about it on X. We searched Mark Kelly's X (formerly Twitter) timeline and discovered that he originally created the on February 22, 2016 (archive):
Scott Kelly ( archive) it the next day and had received over 23,000 views as of this publication:
Our editors then searched the NASA archives and found one to summarize of the #SpaceApe debacle posted by the space agency on February 4, 2020. It confirmed other news reports stating that Mark Kelly had arranged for the suit to be sent from Earth to his twin brother aboard the ISS:
To surprise astronaut Scott J. Kelly for his birthday on February 21, 2016 during his one-year mission aboard the ISS, his twin brother, astronaut Mark E. Kelly, arranged for the delivery of a life-size gorilla suit to the station. In addition to some gentle shenanigans while wearing the gorilla costume that he posted on social media, such as chasing down fellow Expedition 46 crew member Timothy N. Peake via the Destiny module, [Scott] Kelly also recorded some educational videos dressed in the non-standard attire.
As Scott Kelly told in January 2022 (archive), the entire stunt was planned - and his fellow astronaut Tom Peak, who also appeared in the video, was not surprised:
That was all staged. That's why he's floating around, swimming in the air, we wanted it to look funny.
It was the end of my year in space...so you need a little humor.
Following on from his alien primate fame, Scott Kelly even posted an educational post to
Mark Kelly, who is a US Senator from Arizona retired from NASA and the US Navy in June 2011 after a decade in spaceflight, according to his NASA profile . Scott Kelly was first selected by NASA in 1996 and retired from the space agency after twenty years of service.
Sources:
"Astronaut Scott Kelly reveals the real story behind the video of him in a gorilla suit aboard the space station." Peoplemag, https://people.com/human-interest/astronaut-scott-kelly-reveals-real-story-behind-viral-video-gorilla-suit-aboard-space-station/. Accessed March 14, 2024.
"Home | U.S. Senator Mark Kelly of Arizona." Senator Mark Kelly, https://www.kelly.senate.gov/. Accessed March 14, 2024.
" https://Twitter.Com/CaptMarkKelly/Status/701918950678892544." X (formerly Twitter), https://twitter.com/CaptMarkKelly/status/701918950678892544. Accessed March 14, 2024.
" https://Twitter.Com/StationCDRKelly/Status/702239878323372032?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E702239878323372032%7Ctwgr%5E28e50119a5b24c06872 c5a7dc595c6a3daf1957b%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fwww.Iflscience.com%2Fthis - Is-the-actual-truth-behind-the-Gorilla-in-Space-Prank-62300." X (formerly Twitter), https://twitter.com/StationCDRKelly/status/702239878323372032?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E702239878323372032%7Ctwgr%5E28e50119a5b24c06872c5a7 d c595c6a3daf1957b%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fwww.iflscience.com% 2Fthis-is-the-real-truth-behind-the-gorilla-in-space-joke-62300. Accessed March 14, 2024.
" https://Twitter.Com/Stationcdrkelly/Status/919971753320964097?Lang=en." X (formerly Twitter), https://twitter.com/stationcdrkelly/status/919971753320964097?lang=en. Accessed March 14, 2024.
" https://Twitter.Com/Todd_Spence/Status/1480256216618049537?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1480256216618049537%7Ctwgr%5E7b348055a786f813ed5 a8d9831c9afc44337d843%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fpeople.com%2Fembed%3Furl %3Dhttps3A2F2Ftwitter.com2Ftwitter2Fstatus2F1480256216618049537id%3Dmntl-Sc-Block_1-0-16-iframeoptions%3De303DdocId%3D5989513." X (formerly Twitter), https://twitter.com/Todd_Spence/status/1480256216618049537?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1480256216618049537%7Ctwgr%5E7b348055a786f813ed5a8d9 831c9afc44337d843%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fpeople.com%2Fembed% 3Furl %3Dhttps3A2F2Ftwitter.com2Ftwitter2Fstatus2F1480256216618049537id%3Dmntl-sc-block_1-0-16-iframeoptions%3De303DdocId%3D5989513. Accessed March 14, 2024.
20th Space Station: Celebrating Birthdays on ISS - NASA. February 4, 2020, https://www.nasa.gov/history/space-station-20th-celebrating-birthdays-on-iss/.
