The Florida university student - who can be seen beaming out of Ellen Degeneres's epic selfie with a quirky flat top and thick rimmed glasses - posted a montage of himself in a photo with Justin Timberlake and Janet Jackson.
The mock up showed Peter supposedly taking part in the songstress' Superbowl wardrobe malfunction. Besides it he wrote: "Apparently I'm photobombing everything #lmao #icant #dead hahahahaha," using Twitter shorthand for something that's just too funny for words.
Peter, 20, has been accompanying Lupita on the awards circuit for the last six months, having his picture taken with the glitterati.
He's been sharing snaps with his 4,500 instagram followers of himself with Samuel L Jackson, Jamie Foxx, Idris Elba and even Sir Alex Ferguson.
In an interview with BBC radio Fergie revealed that he gave Lupita a pep talk just before she picked up a gong for playing Patsey in Steve McQueen's 12 Years a Slave.
"I spoke to some (of the stars) the night before at a party in Beverley Hills," said the former football manager. "I was chatting to Lupita and wished her all the best and she won."
Peter was overwhelmed by his support, tweeting the picture with Sir Alex and the message "You know you have arrived #tears #legend".
At Sunday's Oscars he seized his chance when Ellen beckoned stars like Brad Pitt, Angelina Jolie and Jennifer Lawrence into her photo.
His infectious joie de vivre won the approval of Girls creator Lena Dunham, who tweeted: "Who else thinks Lupita's brother should have his own show?"
He also made it on to The Simpsons when creator Matt Groening shared his cartoon version of the image showing Bart being kicked out of the frame.
"'The ugly true story of that Oscar selfie can finally be told! Let's break Twitter again. Look for Bart," said the accompanying message on the show's official feed.
Oscar-winning Lupita said she was proud of her photobombing brother, adding: "That was his win for sure. He got into the most famous selfie in the world. I am glad I could have facilitated that."
When the 12 Years a Slave starlet appeared on Ellen's TV show the following morning, the chat show hostess also commented on Peter's moment of glory.
"Your brother is very famous now," she said. "You can see him more than just about anybody (in the picture)."
On his social networking sites, Peter has dubbed his sister 'Princess Luppy' and 'Lupiterella' because of her fairytale story.
Meanwhile his twitter feed has the strapline: "Play your song, if you're good enough the world will love you". It seems the world is ready to do just that for Nyong'os.
Who else thinks Lupita's brother should have his own show? OK, summon me when HER wins!— Lena Dunham (@lenadunham) March 3, 2014