Jimmy Butler Rocks Emo Hairdo For Fall Out Boy Music Video

Emo Jimmy Butler is back in a big way -- the Miami Heat star is heavily featured in Fall Out Boy's latest music video ... playing the role of a dancing cowboy!!

Butler -- who looked more like Jimmy Heat World during Miami's media day thanks to his hilarious haircut -- brought the look back in the visuals for "So Much (For) Stardust," which show him grooving while rocking an all-purple, bedazzled look.

The first half of the video is all about Butler ... before his character shakes a magic 8 ball and the band's bassist, Pete Wentz, pops out in a beige costume that rivals the hooper's ensemble.

Fans -- who are cleverly dubbing Butler "Heat Wentz" -- are loving the project ... praising the two for movin' and groovin' together in the latter half of the song.

The cowboy part is natural for Jimmy -- especially considering he's been open about his love for blaring country music and his plans to drop his own album.

When he spoke with reporters at media day ... he explained he wanted to be "one with my emotional state," but he quickly switched back to his regular cut shortly after.