'Wonder Years' star Danica McKellar celebrates 51st birthday with authentic no-filter selfie

Danica McKellar celebrated her 51st birthday with a bared-faced selfie.

"This is 51!" the Great American Family star wrote on her Instagram last weekend while wearing a red flannel shirt, cross necklace and her wavy hair down. She continued, "No makeup, no filters, just front-facing lighting and a healthy lifestyle to look - and more importantly - feel the best I can."

The "Wonder Years" alum said she spent her day doing puzzles with her family, working out, and she even did a cold plunge in the ocean...