The most generic Halloween plot is when a character gets scared and spends the rest of the episode getting back, and that's exactly what half of "The Good Guy Fluctuation" consists of. Sheldon is turned into a stock "Halloween character," who makes himself into a fool trying to scare others.
The other plot was a bit better since it dealt with a serious matter and was funny in its own right. Still, it didn't negate how useless and dumb the other plot was. Hopefully Priya and Leonard are done for good. Leonard made out with a girl and Priya slept with her ex. The story has gone on far too long already and needs to be over. I'm not confident it is over, though.