Ruby offers monkey patching methods in order to change the behavior of a library if there's no better way.
We can call the method we're overriding inside our monkey patch:
class Foo def bar(argument) 'Hello' + argument end end module FooExtensions def bar super(' in my') + ' World' end end class Foo prepend FooExtensions # the only change to above: prepend instead of include end Foo.new.bar # => 'Hello in my World'
As mentioned, monkey patches are usually a threat to your code quality, so try to avoid them if possible.
For a better understanding have a look at this article.