The Naked Gun movies all were shot open matte. The widescreen framing on the DVD of the first film is slightly off, as you can see a sliver of the bra Priscilla Presley is wearing when she's supposed to be naked.
Ironically, the filmmakers on the commentary track mention how visible the bra was in old fullframe transfers. I guess they couldn't see this on the monitor they were using because of overscan?
No idea if this is fixed for the Blu Ray.