You will begin with this Scratch cat, the number one on his forhead symbolizes its level. Hit request, and a clone of it will pop up. Drag it to the original and you will have a level two. Continue requesting and merging til you got level 5, wich is the max. When finished you should have all the versions of the cat at once.
I'd like if you remixed this and made a game out of this function. That was after all the point. Inspiration taken from the mobile game Merge Plane (On Google Play, not scratch). Just a showcase. All the bugs i came across i dont know how to fix.