This year (and for that also the coming years) a lot of people will visit the West of Flanders in remembrance of the first World War, 1914-1918.
This is of course not funny at all, but these t-shirts who want to help people to understand the local dialect are really funny. And btw, they’re actually correct. The ‘Behinners’ is also an inside joke as the idea is that people from West-Flanders have an issue with pronouncing the G and the H.

If you want to learn a bit more of our great language, do check this urban slang dictionary in the making.