The Metal Gear Solid main theme used in the first MGS, Sons of Liberty, The Twin Snakes and partially in Snake Eater was removed from Portable Ops shortly before its release because of a potential plagiarism.

Someone on the Internet found a song called "The Winter Road" by the Russian composer Georgy Sviridov which strongly resembled the theme composed by TAPPY.

When Hideo Kojima heard it and became aware of the similarities between the two tracks, he decided to not use the theme again in any future titles in order to evade legal issues.