McDonald's tongue-in-cheek promotion comes with the launch of three different Big Mac sizes: Grand Big Mac, Big Mac and Mac Junior.
The restaurant chain is holding a competition where fans of the Big Mac sandwich are invited to post an ode to the burger on social media.
If you want to try out the new sizes you'll need to be quick as they are only on the menu until Tuesday, March 20.
For diners with a smaller appetite however, the Mac Jrn is a smaller version of the traditional Big Mac burger which includes one beef patty, a slice of cheese, and the sauce.
A McDonald's spokesman said: "Due to the overwhelming popularity of our new Grand Big Mac some of our restaurants experienced higher than expected demand resulting in the burgers being sold out for a short period of time".
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It has 400kcal per serving and costs £2.19.
'We know a lot of our customers will remember the 1974 launch of the Big Mac in the United Kingdom and have continued to enjoy the burger and pass the Big Mac love on since then, it remains our most iconic burger!'
Where can I buy the new Big Mac burgers?Either the fast food chain has severely upped its Happy Meal prize game, or something is afoot.
The Mac Jr and Grand Mac were already tested in 2016 in OH and Dallas, because they are "beef-centric areas".