quote:

http://starwars.wikia.com/wiki/Millennium_Falcon

The original model for the Millennium Falcon was changed at the last minute because it too closely resembled the Eagle Transporter ships used in the Space: 1999 television series. The replacement is said to be based on a half-eaten hamburger next to an olive on a toothpick held by George Lucas, which led to staff at ILM refering to the Falcon as "the Porkburger" [34]. Ralph McQuarrie's original design was modified to become the Blockade Runner starship seen at the beginning of Episode IV, and the original design was also used for the diplomatic transport that brings Qui-Gon Jinn and Obi-Wan Kenobi to Naboo at the beginning of Episode I.

The cockpit design of the Millennium Falcon is also heavily based on the design used in the famous B-29 Superfortress.[source?]