You're partly right. Fixnums don't have a metaclass (or virtualclass) because they're actually "immediate". So you can't say 123.extend(Something) because 123 isn't really a full Object.
That's just to say that there aren't multiple "2"s. But 2 itself is still an object, pointing at its Fixnum class, which has all the normal Class and Object semantics.
Yeah. Conceptually, you can think of the difference as whether or not there can be two copies of something. There can only be one copy of a Symbol, Fixnum, true, false, and nil. This means that true == true, and true.dup #=> error.
