It's not his pal Akeem but an uncredited star in a cameo appearance who really saves Robin Hood in the end. And now, thanks to the magic of the VCR, you can salvage those lemon rental movies by inserting your own cameos from superior films. All you need are a blank tape, two movie cassettes, and two VCRs (with standard cables running from one's ''out'' jack into the other's ''in''). Some examples to get you started:
My Dinner With Andre
Hit lady Anne Parillaud, in La Femme Nikita's
restaurant-assassination scene, interrupts Wally Shawn and Andre
Gregory.
The Sheltering Sky
Kit and Port get over their endless desert
ennui when Hope and Crosby perform ''Moonlight Becomes You'' from Road
to Morocco.
The Doors
Jack Nicholson, as the grinning acidhead rock musician
in 1968's Psych-Out, pops in as a member of Jim Morrison's wacky
crew.
The Godfather Part III
Al Pacino, in any scene from Scarface,
emerges as Michael Corleone's illegitimate, drug-dealing Cuban son.
Ghost
The cast of Topper (Cary Grant, Constance Bennett) appears
as Patrick Swayze's pals beyond
the pale.

