Shortly after its release, the originality of the song was questioned in the Dan Gaffney Morning Show of Delaware based radio station WGMD 92.7. The presenters alleged that the Chili Peppers had plagiarized Tom Petty and the Heartbreakers' 1993 hit Mary Jane's Last Dance. To demonstrate, they presented audio snippets of both songs, both side by side and simultaneously (i.e. on top of each other) several times. They stated that the chord progression, key, tempo, and the lyrical theme of the songs (both produced by Rick Rubin) showed "startling similarities" and urged listeners to "decide for themselves".
Some have dismissed this as a publicity stunt by the DJ's. Posters on the official Chili Peppers message board have pointed out that they sped up "Mary Jane's Last Dance" to more closely match the tempo of Dani California. It's also been pointed out that while the first 8 bars of both songs sound similar, the chords are not exactly the same, with "Mary Jane's Last Dance" being "Am, G, D, Am" and "Dani California" being "Am, G, Dm, Am". University of Chicago musicologist Travis Jackson said the songs' chord progressions were similar, but were a "pretty standard groove" in music
and not necessarily evidence of copying.
Spin magazine readers voted in a June 2006 poll on the similarities of the songs: "We asked if you thought the Chili Peppers ripped off Tom Petty for their new single. The outcome might surprise you. The votes are in! As of press time, 49 percent of you felt the Chili Peppers' "Dani California" bites "certain musical elements" from Tom Petty's 1993 hit, "Mary Jane's Last Dance," while 46 percent said "Dani" was totally original. An on-the-fence five percent of readers weren't quite sure." Spin also posted an audio comparison of the two tracks.
In an interview with Rolling Stone magazine, Petty denied rumors that he planned to sue the Chili Peppers and said "I seriously doubt that there is any negative intent there. And a lot of rock & roll songs sound alike.