Like patching of classes, you can also patch single objects. The difference is that only that one instance can use the new method.
Example: Override a string object to provide parsing to boolean
s = 'true'
t = 'false'
def s.to_b
self =~ /true/ ? true : false
end
>> s.to_b
=> true
>> t.to_b
=> undefined method `to_b' for "false":String (NoMethodError)