A while ago a 15-20 line patch was committed, which added the methods Array#second, Array#third, etc. These methods were added as syntactic sugar, in order to complement the built-in Array#first. What followed was a huge uproar on Reddit; people called the patch "bloat", claimed that Rails is growing into an uncontrollably large monster, etc. The uproar was not unlike the recent uproar about Coffeescript in size. DHH made fun of that by adding Array#forty_two.

It was added as a joke in response to the controversy on reddit about the original commit.