The billboard read "Rocky and his Friends" but the letter Boris stole were the letters "r" & "s" so the billboard wound up saying "Rocky and his Fiend" to which the commercial voice said "Now wait a minute, that's supposed to be friends. Who stole those letters?" To which Boris replied "Nyahehe Never underestimate the power of a snook."
Here is the commercial on YouTube: http://tinyurl.com/18r