This German guy wanted to marry this Polish lady, but Poland had a law that you have to be Polish in order to marry someone that is Polish, so, in other words, he'd have to have 50% of his brain removed. So he goes to his doctor and says, "I've just got to marry this woman, I love her so much..."
So the doctor says, "Well, it's risky, but okay." So into the operating room they go for the brain removal procedure.
Later, when the German guy wakes up, the doctor comes in and says, "We are verrrryyyy sorry, but we accidentally removed 75% of your brain instead of 50%."
The guy looks up and says, "Mama Mia!"