Follow that egg is season 9

Those are all season 9, so i'll assume that that's what you meant. My least favourite from season 9 were Mr. Garrison's Fancy New Vagina, Wing, Free Willzyx, and Marjorine

“Series 10” episodes?

You mean the ninth? Mine were Two Days, Closet, Willzyx and Bloody.

It seems you meant season 9 which in that case are: 'Erection Day' and 'Mr Garrison's Fancy New Vagina' the latter being in my bottom 3 South Park episodes of all time

Best friends forever, mr. garrison's fancy new vagina, ginger kids

Free Willzyx… So depressing.

Season 9: Erection Day, Season 10: Stanley’s cup

But only if we’re talking least favorite because I dislike none lol