A laugh-out-loud section of the show would probably have gotten a lot more appreciation were it not for what came later:

Molesley's moments of glory! I had to back up and verify that, yes, he was dancing by himself in the corner. And then when he really got going, wow! Who knew Molesley had such a wild side?
I also rather enjoyed the dynamics between the ladies' maids, and the fact that O'Brien was a fairly normal character in this episode.
Also, it was nicely realistic that she actually noticed that her drink was spiked and gave it up after the first sip. Why is it that in some movies when that happens the person goes ahead and drinks the whole thing without seeming to notice? O'Brien's smarter than that.