I sat next to the Duchess at tea.
It was just as I feared it would be:
Her rumblings abdominal
Were truly phenomenal,
And everyone thought it was me!

A variation with "thought" instead of feared and "abominable" instead of phenomenal is reported as a misattribution in Paul F. Boller, Jr., and John George, They Never Said It: A Book of Fake Quotes, Misquotes, & Misleading Attributions (1989), p. 132