Pat into a 9 by ... rhubarb layer. Prepare pudding according to package directions and spread on cream-marshmallow layer. Sprinkle left over crumb mixture on top. Refrigerate.
Combine UNdrained fruit in bowl. Stir in pudding mix. Store in refrigerator 1 hour or longer. Fold in marshmallows and Cool Whip. May be ... be used, if desired.