Is it possible to change the class of a Ruby object?

Is it possible to change the class of a Ruby object once it has been instantiated, something like:

class A
end

class B
end

a = A.new
a.class = B

or similar.

(the above code does not run as class is a read only variable)

I know this is not advisable, a bit strange, and not something I plan on doing, but is it possible?