What does as welcome as a skunk at a lawn party mean?

Answer 1

Unless it has had its musk gland removed, a skunk would not be very welcome at a lawn party because it would be frightened by human presence and might because of this spray to protect itself from perceived danger. This possibility would drive the guests away from the party due to the rancorous aroma a skunk can produce. That would not be the desired situation of either the guests or especially the host. Therefore this phrase is an analogy implying that whatever is "as welcome as a skunk at a lawn party" is very unwelcome.