I agree about Pet-Tik being very consistent throughout the 1999-2000 GP series, but the hype at worlds was about S&Z and S&P. I don't think anyone expected the very consistent S&Z to make 3 mistakes in their LP. In that sense I would call it a shock.
I don't see M&D's 1991 worlds win as an upset. They won the bronze behind B&E in 1990, but everyone could see their potential, and some even thought they should have won the gold over G&G at the 1990 worlds. I think the only shocking thing was that their 1991 LP (Liebestraum) was so beautiful that it seemed like 1000 years ahead of their comedy routine in the 1990 worlds LP.
With Cohen at 2000 Nationals mentioned, I'll mention Naomi Nari Nam in 1999 also. She had only been 4th as a Junior the year before and I had barely heard of her, but her free skate performance is still memorable to this day as one of the most purely enjoyable and exciting performances I've seen.
When Butyrskaya wonEuros in 1998, it was a surprise for sure. I believe it was her first season with Tchaikovskaya, and she turned up a totally different skater, with the stunning Raol diBlasio-program. Suddenly she had a new-won confidence. Slutskaya, two times champion and golden girl of Europe, made several mistakes (and her dress was terrible, like old baroque wallpaper, she changed it for the Olympics. I adored the Russian folk program though, maybe I'm the only one?) Anyway, Maria was fourth at OG, won bronze at worlds. She really had some momentum (at least in Europe), going into the 98/99-season. She won Euros again, her program (though from last year) even sharper and more difficult. It wasn't just about the results, but also the skating itself. Her confidence really shone through. Earlier she was that kind if skater who the judges would never give anything at all. She was known for meltdowns and being insecure. After switching coaches, that changed. Clever move!
Before worlds in Helsinki, I didn't feel it was THAT far fetched that Maria could challenge for gold. I wasn't really surprised when she won, but I was ridiculously happy, I was there live and I cried with joy for her, the VIPs sitting next to us looked at me like I was nuts lol. To me it was a bigger surprise when Kwan sat in her butt in the short program.
How about Gordeeva/Grinkov winning their first gold at World's in 1986? Yes, they were Soviet and that country usually only sent good teams, but they were just world junior champions, both teenagers at their first world's and up against the reigning world and Olympic champions in Valova/Vasiliev. I think most people were surprised at that result.
Funny how we always here about things you've predicted correctly and never about the ones you've gotten wrong *coughFedererwillneverwinanotherGrandSlamcough*
To think that fun is simple fun, while earnest things are earnest, proves all too plain that neither one thou truthfully discernest.
Add to that:
Oksana Baiul winning worlds in 1993 in her first appearance. Her only international competition up to that point was the Europeans 1993 where she placed second to Bonaly. (Oksana did not compete at the Junior level). Nancy Kerrigan was a heavy favorite and she did not even medal.
Ilia Kulik competing in senior Euros for the first time and winning the event was quite an upset too.
For someone who sat in the audience in 1999 Worlds, Butyrskaya´s win was not a chock. It was a rightful decision.
Sarah Hughes's victory at 2002 SLC . For me that was the biggest upset.