Cook the pierogies according to package directions.
Cook bacon in a large nonstick skillet until crisp. Remove bacon; crumble.
Increase heat to medium-high. Add onion, sugar, and thyme to drippings in pan; saute 5 minutes. Stir in peas; saute for 1 minutes. Add pierogies, salt, and pepper; cook 30 seconds. sprinkle with crumbled bacon. Serve with sour cream.