Interesting. I've never heard that part in there before. Lower in pitch, as was pointed out. It is definitely a different sort of bg vocal for the Beach Boys. That wacky Brian does it again. It is interesting that Murry wrote most of the lyrics to this great song (according to Brian on the Warmth of the Sun podcast series), as was also pointed out.
See that's my whole point. He never did anything quite like that, and it's only in that one part, and it's in a song about audible hallucinations. I reallllllly don't think i'm stretching here!
BTW, just to clarify: GREAT SONG. I love it! The more vocals they add each time they 're-release' it, the better it sounds.