So I did some mild digging, because I had to know.
The Dutch song is apparently called the "Horlepiep" which was something that originally came from Scotland, but was brought home by Dutch sailors of the 19th century. And it actually iS IN FUCKING SPONGEBOB!!! 
The Belgian one is a song from the late 90's, or rather, it's a medieval Flemish folk song that a band called Laïs put to music (they were not the first to do it, but it is a banger.)
