In the film, five items are stolen: the Magna Carta, the Turin Shroud, the Imperial Sword of Japan, the Pope's ring and the Pink Panther diamond. When Alfred Molina's character is challenged that they had found everything but the Pink Panther, he protests that 3 out of 4 is not bad, that's 75%. In fact, they had found 4 out of 5 or 80%.
When Clouseau gets his hand stuck in the car door window in the pre-credits sequence, he steps onto a piano on a moving truck. The notes that play are the first four notes of the "Pink Panther" theme.