"Mercy Mercy Mercy" is a great tune, but it was a surprise mainstream hit. It was written and originally recorded in 1966 and had reached #11 on the Billboard charts by 1967. Later it was covered by The Buckinghams and the Mauds, and was on the charts again.
Man has yearned to be able to binge drink sans hangover with the same ferocity as he once wanted to venture to the heavens. Mercy doesn't say it'll eliminate the consequences, but claims it'll help. This is a titanic claim.