Each thing that changes has a specific letter being swapped for another letter. Example: the Y in ANCIENT YUCKY SOCKS has been changed to an L to make it ANCIENT LUCKY SOCKS.

Errata: After this puzzle was published, we realized that "YUCKY" has a second Y, which should change the word to "LUCKL" but that's not a word. Our bad.

Each phrase that is changed is three words long. You'll need another three word phrase where you can follow the pattern established by the bold text.

Y => L
L => E
G => E

From the paranoid tone and the picture, you get the non-abbreviated, three word phrase "UNIDENTIFIED FLYING OBJECT."

Following the rules from the bolded text, you can change the "UNIDENTIFIED FLYING OBJECT" into a "UNIDENTIFIED FELINE OBJECT."