Revealing mistake: When Larry and Richard are dragging the two bodies to the closet the first one lifts up his legs for Richard to put him in.
Revealing mistake: When Larry and Richard put Bernie in the little red wagon, they take him to his golf cart and right before he falls out of the wagon, you see him putting his arm down so he can ease the fall.
Revealing mistake: When Richard and Larry tie Bernie's laces to their own so they can all run together, you can see that Bernie is running along with them because he is bending his legs at the knees at the same time they are and he's supposed to be dead.
Answer: He says the Italian word "cornuto." Basically insulting Bernie for sleeping with Vito's girlfriend, which is why the hit was put on him in the first place.