It could be the alcohol, the lateness of the hour (especially when parties literally go on until dawn) or it’s a cultural thing, but I’ve noticed that different countries have different French sing-a-long favourites.
At midnight the famous C’est Extra parties in Montréal get the entire room singing seven minutes of Gigi L’amoroso by Dalida.
Now, that doesn’t work in the Netherlands because the song, or part of it, is known as “Friet met mayonaise” (yes, one ‘n’), which means “Fries with mayonnaise” by Johnny Hoes. However, the Dutch usually go nuts on Non, non rien n’a changé by Les Poppys and sing the chorus. It’s thanks to them that I got to know the song in the first place.
And then there’s Berlin and Munich, which I’ve played recently. So far, they’re just not the sing-a-long type. Maybe one day.
In Belgium, where I’ve also played, Les Cactus by Jacques Dutronc gets everyone shouting a chorus of “Aïe aïe aïe! Ouille! Aïe aïe aïe!” (Ouch ouch ouch! Ow! Ouch ouch ouch!), while you can hear “Auuuux Champs Élyséeeeees (At the Champs Élysées) when the DJ plays Champs Élysées by Joe Dassin.