Not bad. But what I find is that there is mostly one main joke getting repeated all over again in different ways: Flemish and the flu. This joke is introduced at the very beginning and travels throughout the whole article. It is like a parasite which takes away all the light and food from other good jokes (which you have but don't really develop) in order to get bigger and bigger. This article will be greatly improved if the minor jokes (such as EU, colonies under Belgium, Belgian chocolate, etc.) will get separated from the flu topic and will have more attention paid to them. But your article is funny, anyway.
This is a very good idea to talk about Flemish and present its history the way you did. But here again we return to the same thing I have said in the Humor part. You have only one major idea (flu) and others are unnoticeable because of it.
Prose and formatting:
Generally looks like an encyclopedia article. But some sections have to be rephrased: for example in the 3d sentence the sentence construction confuses the reader (maybe it is a grammar mistake). Also sometimes you overuse the proper names (i.e. Spanish, Flemish, French) in a short part of the article (for example, the word Spanish is used 5 times in the section about origins of Flemish, which is rather a short section). At the beginning of 'Development of Flemish...' you say: "powerful, superpower country". Those cannot be synonyms as they have the same root.
Otherwise, the article has a good construction, interesting and easy to read.
The images give a good impression and the quotes are well-made. But:
The first image doesn't increase the humor of the article.
The second one is fine but it can be made smaller, if you want to add other images.
Good construction, really funny connection with the real history (which is a very good common point of most of your articles).
The article gives a very good impression. The most important area of improvement is the addition of new jokes or development of already existing ones which will lead to the appearance of other important issues not depending on the question of cold and flu.