* (defclass foo () ())

#<STANDARD-CLASS COMMON-LISP-USER::FOO>
* (defgeneric add (foo &rest bar))

#<STANDARD-GENERIC-FUNCTION COMMON-LISP-USER::ADD (0)>
* (defmethod add ((foo foo) &rest bar)
    (list foo bar))

#<STANDARD-METHOD COMMON-LISP-USER::ADD (FOO) {1002CB6FD3}>
* (add (make-instance 'foo) 2)

(#<FOO {1002CB90D3}> (2))
*