"Rainbow Road Medley - Super Smash Bros. UItimate" is a high quality rip of "Rainbow Road Medley" from Super Smash Bros. Ultimate.
Starting at 0:05, elements from "Gangnam Style" are mashed up and pitch-shifted with the advertised track. At 1:03, "Gangnam Style" is switched out for "Gentleman". At 1:30, the saxophone from "New Face" by PSY is pitch-shifted to the track.
The rip loops once at 1:55. From 3:46 to the end, the track is unedited as it fades out.