Freshly shredded cheese works better than packaged shredded cheese in a cheese ball. Prepare the cheese mixture the night before so flavors have a chance to blend. Shape and roll in the crumbled bacon or pistachio nuts a few hours before serving.
In a very large bowl combine cheddar and cream cheese; let stand to come to room temperature (about 45 minutes). Add pimientos, apricot preserves, milk, Worcestershire, hot pepper sauce and about 1/2 of the cooked bacon. Beat with an electric mixer on medium speed until almost smooth.
Cover and chill cheese mixture (and cooked bacon) 2 hours or until easy to handle. Divide into portions; on waxed paper shape into balls. Cover and chill. Roll in bacon bits or pistachios within 4 hours of serving.
Serve with celery, cucumber, apricot and/or toasted bread slices. Makes 18 (1/4-cup) servings.