I have a version of a contrary poem that I learned as a child that is fun for kids, and actually works quite well as a skit or play for a cub scout pack meeting or family reunion with someone reciting the poem as the kids act out the parts. It goes:
Pull up a chair and sit on the floor, And I'll tell you a tale I never heard before.
One bright day, in the middle of the night, Two dead boys got up to fight.
Back to back, they faced each other, Drew their swords and shot each other.
A deaf policeman heard the noise, And came and killed the two dead boys.
And if you don't believe my tale is true, Ask the blind man ... he saw it too.
There are lots of different versions, some that are quite a bit longer. The British Columbia Folklore Society provide some literary and historical analysis of the poem and some variants, and lists a couple other types of nonsense rhymes. Wikipedia has a longer version. This site notes that a version of the poem was used in the movie "The Haunting of Connecticut."