Whoa! Justin Bieber's gettin' flirty with long-time pal Cody Simpson! We thought Miley Cyrus' social media proclamations of love were a bit much, but now Justin's one-upping her with a flat-out offer to double date (aka, swing) with Miley and her new man and him and wife Hailey!

Miley's back home from the hospital and she and Cody celebrated with -- what else -- a shirtless selfie of him and Miley in front of her bathroom mirror to which Justin -- SURPRISE! -- commented, "Ur body is a wonderland. Double date?"

What the?!?!?

The Aussie wrote back, "Text me." It's ON!!!