In a moment that has to be heard to believed, John Lennon's unforgettable vocal on the Beatles' 'Hard Days Night' fits perfectly into the crunchy riff of Motley Crue's 'Girls Girls Girls' from nearly 25 years later. One of the more amazing moments comes when George Harrison's original riff is melded with Mick Mars' molten solo.

Couple it with a video that intercuts classic black-and-white clips of the Beatles with Crue's original 1987 strip-club video, and -- voila! -- you have 'A Hard Girls Night.' Mashed up courtesy of Wax Audio, the song is mind-blowing fun. Coupled with the video, it becomes a study in the way rock -- and groupies -- changed in the intervening years.

The song is also available as an MP3 download via Soundcloud. Some of Wax Audio's recent mashups include 'Stayin' in Black,' combining the Bee Gees with AC/DC; and 'Chemical Driver,' featuring Dio and the Chemical Brothers, among others.