Questions:
1) Is it an official clip?
2) Why did L. Nimoy play in such a movie?
Answers:
1) Yes.
2) Nimoy met Aaron Bay-Schuck (vice president of A&R Atlantic Records), who produced the video with the song "The Lazy Song" from Bruno Mars, in 1985 when he (Nimoy) was preparing to direct Star Trek IV. Bay-Schukc was 4 and 1/2 years old. Nimoy married his mother later, in 1989.
also see: Trekmovie.com