I used to be hardcore Opera fan, and this reminds me of something they did back in the days when Jon von Tetzchner was over there. They released "Opera Bork" edition https://press.opera.com/2003/02/14/opera-releases-bork-editi... because MSN was sending a broken website specifically to Opera, so they spoofed the user agent.
I came to the comments precisely to post this exact link so delighted to see someone beat me to it.
Opera were always so good at giving a window into the world of compatibility testing & challenges - @hallvord in particular had a great blog on my.opera about their work subverting large websites that would block or thwart Opera & other non-IE browsers.
