Ljubljana, Slovenia.
Temperature: -6°C Clouds: Broken Clouds
Maribor, Slovenia.
Temperature: -5°C Clouds: Scattered Clouds
Portoroz, Slovenia.
Temperature: 6°C Clouds: Broken Clouds

Two screenshots from South Park episode 313.
The South Park episode Hooked on Monkey Fonics, which originally aired on November 10, 1999, has a brief, inexplicable shot of Slovenia’s flag. You see it for a split second, before two parents burst into the room of their young, nerdy, home-schooled daughter Rebecca.
Why does she have a Slovenian flag on her door? No idea. It seems entirely random. As far as I can tell.
While stumbling around online looking for clues, I found this comment about it by a slightly angry Slovene:
"since whole family is weird and geek kind - I hate to think as it was meant that this family is originated from my country.Our people are whole different, we are anything but boring as those guys, neighter lame as that.We Slovenians are whole lot different, and I can’t imagine where on earth those assholes that decided to draw that flag on the doors had there mind that day.Stop doing drugs while making South Park and you’ll be just fine, mkay?"
His guess is probably as good as any.