In the bowl of a stand mixer fitted with the paddle attachment, whip the cream cheese and cheddar until softened and well combined.
Add the pimiento onion, bell pepper, Worcestershire and lemon juice, and mix well until all ingredients are fully combined.
Transfer the cheese mixture to a bowl, cover with plastic wrap and refrigerate until firm, about 2 hours.
Shape the mixture into a ball and roll it in the walnuts, gently pressing them against the surface to help them adhere.
Wrap the ball in plastic wrap, and refrigerate overnight to let the flavors meld.
Serve with butter crackers.