Preheat oven to 350°F (175°C).

Cook egg noodles according to package directions and drain.

In a skillet, brown ground beef over medium-high heat.

Add onion, garlic, and bell pepper to the skillet and cook until softened.

Drain any excess grease from the skillet.

In a large bowl, combine the cooked noodles, browned ground beef mixture, pepperoni, pizza sauce, and milk.

Mix all ingredients thoroughly.

Pour the mixture into a 2-quart casserole dish.

Bake in the preheated oven for 20 minutes.

Remove the casserole from the oven and top with shredded mozzarella cheese.

Bake for an additional 10 minutes, or until the cheese is melted and bubbly.