Revealing mistake: In the sequences where Mandrake and Ripper are under attack by the US Army, we see exterior battle sequences in front of the base. However, no matter how many bullets are fired at the building, all the windows remain intact.
Revealing mistake: Matte lines are visible on Major Kong as he falls through the bomb doors.
Revealing mistake: A string is visible on the left wing of the bomber in one of the shots right before it drops the bomb.
Answer: Peter Sellers improvised it. During that scene if you watch the actor playing the Russian character you can see him trying not to laugh at Seller's performance.