The 'Next 2 You' singer, who launched the perfume in New York last week, joined forces with Jimmy Fallon for the black-and-white mock advertisement.
Bieber opens the advert by whispering to the camera: "Someday we'll be together. Someday I'll be next to you... Someday I'll be older and fatter."
Fallon then joins Bieber on screen wearing an identical outfit and sporting the teenager's signature swept hair, whispering: "Someday you'll look like this."
"What happened?" whispers Bieber.
"You just got busy and your metabolism changed a bit," responds Fallon in the same hushed tones.
"I can eat like five slices of pizza and I don't gain an ounce," says Bieber.
"Enjoy it, dude," replies Fallon.
After a brief whispered conversation about the importance of working out and taking care of themselves, Bieber and his future self return to whispering "somedays" at the camera such as, "Someday video games will be an Olympic sport" and "Someday I will get the Mike Tyson tattoo on my face."
Bieber launched 'Someday' in front of the thousands of fans at Macy's in Manhattan on Thursday, where a minor scuffle broke out following a misunderstanding between members of Bieber's security team and a plain clothes police officer.
All proceeds from 'Someday', which is for women, will go to two charities, including Pencils of Promise, which builds schools in developing countries across the world.
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Watch Justin Bieber's spoof commercial for 'Someday' below:
Watch the official advert for 'Someday' below: