Muscles was the name of Michael's pet boa constrictor so it was not opposite of his religion to write that song, it was a clever play on words and he knew what people would think the song was about. When Michael worked with Sir Paul, McCartney was staying at a ranch in California while writing and recording. Michael went to that ranch and stayed with Paul there to work with him. Michael fell in love with that ranch and bought it, it became Neverland.
The sing Somebody's Watching Me was meant to originally for Lenny Kravitz as Rockwell was friends with Lenny Kravitz and he wrote it with him in mind but Lenny Kravitz said Rockwell sing it. So in essence the song could have been Lenny Kravitz, Rockwell and Michael Jackson on one somg together.
