The Block look (named Casillas in Spain) was the 3rd Cartoon Network look in Europe.
The Blocks theme was slightly different and featured blocks featuring cartoon characters from a Hanna-Barbera cartoon, a Warner Bros. cartoon, an MGM Cartoon, or a Cartoon Cartoon going from one place to another.
Each box shows a video clip from the same (or different) cartoon. In each box, a character does an action, when they leave a box, they move to another box or their action is taken over by another character in another box.
However, it appeared back in Europe in early 2002 to early 2006. Weirdly, at the end year of the European version of the era, sometimes the cartoons don't come from any episodes as a clue, as in a 2005-2006 bumper, you can notice the characters and the prop's pop out in the middle of the blocks.
Some of these bumpers were also used in Latin America from 2002 to 2005.
It's counterpart in the United States is YEEEAUHHHH!.