The Hangover star, 42, will marry the 29-year-old on August 11, according to a website which obtained a copy of the wedding invite.

A source told website Celebuzz: "While it has the formal and standard details of who, what, when, where – including Zach's full name Zachary Knight Galifianakis and his fiancée's, Mary Quinn Lundberg – it is also very funny.

"Zach included a drawing of himself and his bride-to-be. He made sure he looked like a little troll, while Quinn is a stunning tall blonde princess."

It is unclear whether Zach ever got engaged to Quinn, who is vice-president and co-founder of Growing Voices, a charity dedicated to giving back to the community.

The comedic actor next appears with Will Ferrell and Jason Sudeikis in 'The Campaign', and 'The Hangover' franchise will continue next year with its third instalment, also staring Bradley Cooper and Ed Helms.

The Hangover III will be filmed in Las Vegas.

While the second instalment in the comedy franchise was set in Asia, the third and final movie will return to its roots in the gambling capital in the state of Nevada.