Ruby

=begin
I guess the best way to explain this is with an example:

class A; def self.foo; 'bar'; end; end
=> nil
class B < A; end
=> nil
A.method(:foo).unbind.bind(B)
TypeError: singleton method called for a different object
from (irb):3:in bind' from (irb):3 from /usr/bin/irb1.9:12:in '

I've tried this on Ruby 1.8.5, 1.8.6, 1.8.7, 1.9.0 and 1.9.1 and I get this behaviour. It works in JRuby however. It's quite trivial to fix. I've attached a patch below, after the application of which Ruby's behaviour is:

class A; def self.foo; 'bar'; end; end
=> nil
class B < A; end
=> nil
A.method(:foo).unbind.bind(B).call
=> "bar"
a = A.new
=> #<A:0x00000000b1d870>
b = B.new
=> #<B:0x00000000b18230>
a.define_singleton_method(:foo){'baz'}
=> #<Proc:0x00000000b10df0@(irb):6 (lambda)>
a.method(:foo).unbind.bind(b)
TypeError: singleton method called for a different object
from (irb):7:in bind' from (irb):7 from ./irb:12:in '

I think this makes more sense.
=end