In this case the "f" changes the word Patrick to Fatrick insinuating that the person named Patrick is Fat.
Its simpler using this method than just saying Pat is Fat.
Fatrick is quicker, simpler, and actually quite effective.
FATRICK STOP EATING FRIED CHICKEN.
FATRICK LIKES BUTTER.
DONT SAY PAT IS FAT JUST SAY FATRICK!
" MOM patass ate all our food"