Spread the peanut butter with the Samurai sword

The story:

I was driving in the car with my fiance, when China Grove came on the radio. I started singing along with the song. When it came to the afore mentioned line, I sang what I thought were the right words. Well......my fiance looks at me and says, "What did you say?". So I repeated what I had sung, and I thought she was going to rupture something she was laughing so hard.