Have you seen Finnish students walking around the city in their overalls, ("haalarit") filled with patches and colors? What's going on, what are these weird partypants?!
Wearing overalls is a very big tradition among students in Finland. They represent you and your fellow students as a collective, especially since every study field has its own overall color and/or design. Overalls come in all colours. Blue, black, white, yellow, green, red, pink... You can tell who belongs to your group just by checking out his /her overalls colour. And if you have an overall, you are most likely to have badges ("haalarimerkki") on it too. Plain overall just happens to looks weird, and besides that also badges have meanings. They tell where you have been, who your friends are, what you like, which team you support... Also other party gear - like handcuffs, whistles and bottle openers - can be attached to your overall. It is also quite common thing to exchange parts of your overall (usually sleeve) with other students. That is to show love, friendship, side subjects or even having two main subjects.You can see people wearing them in every major student happening, like parties, meetings, excursions to other cities, Wappu, etc.
Finland is not the only country in the world having such a strange party wear. The overalls tradition is around 30 years old. And just like so many other student traditions of ours, our Swedish student cousins are behind this tradition as well.
Just remember - your overalls should never be washed ;)
To read more about the overalls see the wikipedia article
Now it will possible for you to get ESN Finland overalls which will identify you and hundreds of other exchange students in Finland!