I think it was Chanel No 5.
Edited: I found this which appears to corroborate my initial thoughts, but which places the ad in 1994. Still, might be the one you remember ...
In 1994, the Arnell Group created an innovated TV spot entitled "Marilyn" starring actress Carole Bouquet sitting amidst the crowd of theatergoers. When she splashed on the enticing fragrance of Chanel No. 5, the actress morphed (via modern video technology) into the image of Marilyn Monroe who began to sing "I Wanna Be Loved By You." [/code]
1980s perfume advert
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