"Fun Toungue Twister!" joke

Here's a fun tongue twister.
Read the following list and then follow the instructions at the end.
Read it LOUD and REAL FAST... see if you can do it!
DON'T read the instructions until you get it right!!!

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 fool cat
This is busy cat
This is for cat
This is forty cat
This is seconds cat
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Did ya do it? Now go back up and read the third word in each line starting from the top to the bottom: )