"Ooooooh maaaaaaa god! Get inside ma belly!" one fan wrote.
Another said: "Date night every night!"
One fan even said the return of the Double Down could rekindle a former relationship.
"I know we've drifted apart, but I deeply miss our romantic dates at KFC gazing into each other's eyes as we chow down on our delicious Double Downs. It was the best time of my life, let us relive the magic together again."
"Want to make the flight over the ditch with me to wrap your lips around these one more time?" a KFC lover asked his fellow Australian friend.
Another KFC regular was buzzed about the new flavours but hoped the burgers wouldn't be as sloppy as previous years.
"Finally, good combinations. Now, let's hope they don't look like they've been run over with a car this time," the fan wrote.
The prices of the three Down Downs vary, with the Original priced at $9.90, Bacon Lovers $11.90 and Zinger Supercharged $10.90, KFC confirmed.
"The hotly anticipated return will be here for a limited time only," a KFC spokesperson told the Herald.
The Double Down was first released in New Zealand in 2011 amid much fanfare and criticism from health advocates.
It has been the subject of numerous media stories focusing on its fat-laden content. In terms of nutrition, it compares with other chain burgers, such as the Big Mac.
ARTERY CLOGGERS
Double Down Sandwich: 604 calories, 34.4g fat, 1380mg sodium
McDonald's Big Mac: 491 calories, 26g fat, 1080mg sodium
Burger King Whopper: 663 calories, 37g fat, 1017mg sodium
Chicken & Bacon Ranch Subway: 456cals, 21.3g fat, 1200mg sodium
Pizza Hut Meatlovers (per slice): 202cals, 7g fat, 537mg sodium