La cucaracha, la cucaracha...

"The cockroach", it means - the name given to the Mexican revolutionary army, but also to a large black beetle. These children had found a cockroach and were shepherding it to the side of the road - and were singing the first four words - all they knew, probably - of La Cucaracha...

https://www.youtube.com/watch?v=iABtli2GBnY