The man in right field for the Miami Marlins has "Stanton" written on the back of his jersey, but the name on his baseball cards will be changing, according to the Associated Press.
... on Wikipedia and Baseball-Reference.com both list him as Giancarlo -- as does his baseball bat:
If you zoom in and push your face up to the screen, you'll see the bat says "Giancarlo," right there in nice gold letters. It's not clear when the picture was taken or put on Twitter, but the original file name suggests last month. He could have been hinting at this new development for weeks, and it looks like his bats haven't always said "Giancarlo" -- two game-used bats from Hall of Fame Memorabilia clearly have "MIKE STANTON" burned into them.