|This is an April Fools' Day version of Mouse Y (value). Please don't take it seriously. You can find the original here.|
The mouse y is one of the two fake coordinates that kaj uses to send the scratch team to the other side of the world. He put the word mouse in the block to trick the scratch team into looking for mice when really, they're not there. If there is actually a mouse, kaj will set mouse y to at least 10000 for them to follow (just so he can steal the power units).
There is another block that kaj uses. It's pretty obvious because of the same colour, shape and size.
The mouse x block however, means NO MOUSES as x means no. The scratch team then fights for no reason because they love mice. (again, for the power units)
A common use of the mouse y block is
- a hacker project
Lucky him! kaj has his own project that hacks the scratch teams location when he's online. To me, this is actually useful.
Nothing complex, just 9 TOTALLY random blocks
when green flag clicked repeat until <not<kaj online>> set [scratch team v] to (mouse y) go to x: (anywhere) y: (scratch team) set [power units v] to  end
The x value can be anywhere, meaning that the team could be in Felidaepia (The cat version of Philadelphia), and the next moment they could be on the planet that Gobo's "friends" appeared.
So, moral of this article: Always use the mouse y block to steal power units