Dr. Seuss' lost tounge twister

Dr. Seuss' lost tounge twister
see if you can do this:
This is this cat
This is is cat
This is how cat
This is to cat
This is keep cat
This is a cat
This is dumbass cat
This is busy cat
This is for cat
This is forty cat
This is seconds cat.
Now go back and read the THIRD word in each line from the top. Betcha you can't resist passing it on.