RCPrince, you are correct, Ravi Shankar did not play sitar on WYWY, that was George. There was another debate earlier on here about just who did play on While My Guitar Gently Weeps, but I'm pretty sure that was Clapton (it sounds like Clapton to me, and Clapton is listed on the credits, so I'd conclude it was Clapton). Further, Harrison did play on Badge -- Do you remember what his pseudonym was?
However, Clapton was not the first "guest" instrumentalist on a Beatles song.
However, Clapton was not the first "guest" instrumentalist on a Beatles song.