From the start of his 40-year career in rock, Elton John has been a collaborator -- but some of his partnerships make more sense than others. When he was still known as Reginald Dwight, John replied to a newspaper ad in 1967 and was handed a stack of lyrics by Bernie Taupin, another up and comer. That began a legendary songwriting collaboration that still exists today. But not all of John's collaborations have been quite as successful ... or expected. Here are 10 of his strangest.

  • Sylvester Stallone

    'Measure of a Man,' from 'Rocky V' (1990)

    Elton John's not at the top of the list of folks you'd expect to record the closing credits tune for a Rocky flick. And yet, he performed 'Measure of a Man' as the emotional climax of 1990's 'Rocky V,' playing under black and white footage from across Sylvester Stallone's Rocky saga. What makes this collaboration a bit stranger is that it's a rare recording by John of a song that he himself had no hand in composing. Instead, 'Measure' was penned by Alan Menken, best known for his work on Disney animated films from the '90s like 'The Little Mermaid' and 'Beauty and the Beast.'

  • Elton John

    'Flintstone Boy,' 1978 B-side

    From the start, Elton John has insisted that he's not lyricist. “I’ve tried, but I can’t,” John told BBC Radio 4 in 2013, “and I don’t want to.” 'Flintstone Boy,' featuring both his music and lyrics, makes it easy to see why. The refrain states simply, "Please don't worry 'bout the flintstone boy/He's all right with me." It's a far cry from "My gift is my song, and/This one's for you," that's for sure.

  • Eminem

    'Stan,' performed live in 2001

    Eminem went into the 2001 Grammys with a slew of nominations for his 'Marshall Mathers LP' -- and a cloud of controversy around his songs, which were considered by critics to be homophobic. One of the few in the gay community to stand behind the rapper was Elton John, who viewed the lyrics as coming from Eminem's satirical alter ego Slim Shady. John joined him on stage, playing piano and singing a melodic hook originally recorded by Dido. The pair have remained friends; John provided support when Enimem was fighting an addiction to prescription drugs, and the rapper sent John and partner David Furnish a wedding present on the occasion of their civil partnership in Britain.

  • Tupac Shakur

    'Ghetto Gospel,' from 'Loyal to the Game' (2004)

    Elton John's collaboration with Tupac Shakur was more of a passive effort. Appearing on one of the rapper's posthumous releases in 2004, the song was produced by John's pal Eminem and leveraged a sample from 'Indian Sunset,' a deep cut on 1971's 'Madman Across the Water.' John has said he was flattered, calling Enimem's effort at melding his work with Shakur's "just genius."

  • Queens of the Stone Age

    'Fairweather Friends,' from 'Like Clockwork' (2013)

    Elton John took the initiative in working with Queens of the Stone Age, reaching out to Josh Homme personally. "He called me on the phone and it took me a minute to work out if I was being punked or not," Homme told NME. "He came in and we tracked a rock song live together, which was a wonderful experience. That is what collaboration is all about, learning something from someone else and maybe reminding them of something they enjoy too. To experience that with Elton was wonderful."

  • Thom Bell

    'Mama Can't Buy You Love,' from 'The Thom Bell Sessions' (1979)

    Producer Thom Bell was one of R&B's most successful producers; Elton John was coming off a run of six consecutive No. 1 albums in the U.S. That probably made a 1977 collaboration seem irresistible. In practice, however, their egos almost immediately clashed. Only six tracks were finished; three of them didn't see release until more than a decade later. They did manage to eke out one hit single, 'Mama Can't Buy You Love,' when a few of the tracks were officially released in 1979.

  • Anne Rice

    'Lestat: The Musical,' 2005

    For all of Elton John's Broadway success, his lone theatrical co-write with Taupin -- 2006's poorly received 'Lestat: The Musical,' based on Anne Rice's 'Vampire Chronicles' novels -- was a flop. The project failed to coalesce on the White Way after a successful tryout run in San Francisco, and disappeared. A cast recording was created, but was never officially released. Demos of the songs by John himself have leaked, however, and offer a tantalizing glimpse at what might have been.

  • 'South Park'

    'Wake Up Wendy,' from 'Chef Aid: The South Park Album' (1998)

    In a tip of the hat to a fictional storyline that had the 'South Park' character Chef introducing Elton John and Bernie Taupin, they returned the favor by performing a song written just for this album. John also guest starred on the episode in which 'Chef Aid: The South Park Album' was introduced. "Every week, we'd sit down and watch 'South Park,'" John once said. "I love the irreverent humor."

  • Brian Wilson

    'How Could We Still Be Dancing,' from 'Gettin' In Over My Head' (2004)

    Elton John and Bernie Taupin have always worn musical influences like Brian Wilson on their sleeves. Their 1972 hit 'Crocodile Rock' borrowed heavily, for instance, from the Beach Boys' core sound. A few decades later, John completed a circle by appearing as a guest star on this Wilson solo song.

  • Tammy Wynette

    'A Woman's Needs,' from 'Duets' (1993)

    Beginning life as a Christmas album, this project quickly expanded to find John pairing with artists as diverse as Leonard Cohen, Don Henley and RuPaul. A collaboration with Tammy Wynette, however, stole the show. Singing on the John/Taupin original 'A Woman's Needs,' they effortlessly settle into a classic vibe that recalls Wynette's legendary cuts with George Jones. Pedal steel and delicate backing vocals set a perfect stage for a late-career highlight for one of country music's first ladies. The tune would also appear on Wynette's own 'Without Walls,' a year later.