Pizza Hors'douerve

8 oz pkg. cream cheese
1 cup ketchup
1 small can shrimp
1 1/2 Tablespoons horseradish
1 green pepper, chopped
1 tomato, chopped
1 small can black olives
scallions, chopped
8 oz shredded mozzarella
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Spread cream cheese over 12" pizza pan and set aside in refrigerator. About 1 hour before using, combine ketchup, shrimp, horseradish, and spread over chilled cream cheese. Top with green pepper, tomato, olives, scallions to taste, sprinkle with 8 oz shredded mozzarella. Serve with crackers.