Pistachio Pudding

1 pkg. pistachio instant pudding mix
1 20 oz. can crushed pineapple, undrained
1 lg. carton Cool Whip
1/2 c. chopped pecans (optional)
1 cup miniature marshmallows

Mix pudding mix and pineapples well. Fold in Cool Whip. Add marshmallows and pecans (if desired). Chill.