This article contains plot spoilers for the 2017 series of Twin Peaks.
"My family, my friend, I've criss-crossed this great land of ours countless times. I hold the map of it here, in my heart, next to the joyful memories of the carefree days I spent, as a young boy, here in your beautiful town of Twin Peaks."[src]
At age 24, after various travels, Wally returned to his hometown of Twin Peaks to pay his respects, to his godfather, Sheriff Harry S. Truman because of his illness. He also gave his parents his blessing to turn his childhood room into a study. When his mother asked him about his travels, Wally made a speech, speaking in a Marlon Brando impression.
Andy says that Wally was born on the same day as Marlon Brando, which would give Wally the birthdate of April 3, 1990, meaning that Lucy's pregnancy lasted for over a year or that Wally is a different child altogether, especially if the year of the revival is actually 2016, more than 27 years later.