by JULES FEIFFER
Jules Feiffer may be mad, but it is our good fortune that Knock Knock is happily incarcerated in off-off-Broadway's Circle Repertory Theater. This is a kooky, laugh-saturated miracle play in the absurdist tradition. It is as if someone had merged The Odd Couple and The Sunshine Boys and peppered the mix with Kierkegaard and the Marx Brothers. Nor is that all. The unifying element is Jewish humorskeptical, self-deprecating, fatalistic and with an underlying sadness that suggests that all the mirth is a self-protective mask hiding imminent lamentation.