Reading your reference, I had to look for this song, and I found it here.
On the surface, it's a light and inconsequential video, but there are odd disputes in the comments section that I don't understand - don't understand because I don't read Czech very well and because I don't know the context of this song and video. Maybe I'm misinterpreting the antagonism in the comment section, or maybe it can be explained by the fact that some people are inexplicably nasty online in both English and Czech.
In any case people run across this post, if they know anything about it, I'd love to read additional comments here.
***I did find some context here.
Edited: Fixed link. Thanks VladaFu. That's what I get for trying to be clever with formatting code.
While ON should have been accepted, IN has higher occurrence.