We know Wayne's middle initial from a letter that is shown in episode 26.
Old Wayne is played by Sam Bernstein 14. 

In real life:
Jason Hervey 

• Jason Hervey appeared in his first commercial at the age of four-and-a-half and made his TV acting debut at the age of six on the series "Sweepstakes." At the age of seven, he appeared in a Levi's jeans commercian that won the Clio Award. Hervey himselfs said that he owes his "whole entire career to the 250 commercials [he] did while growing up."
• On Nov 10, 1998, he appeared in TV series "Working" aside of his Wonder Years' brother Fred Savage who has the leading role in "Working". Danica McKellar (Winnie) was also a guest star in this TV series but in a different episode.
• Jason Hervey had a long-lasting relation with Dawn Bailey who was 21 at that time ("an older woman"). They both lived with their own families - Hervey had rent an apartment in an L.A. complex owned by his parents, who lived downstairs - but tried to spend all their free-time together. They enjoyed going dancing, out for a meal and cycling. Jason said Dawn was a beautiful woman, an ex-bikini pattern, but was then a secretary. 
• Currently, Jason Hervey is active Hollywood both as a producer of sports vignettes and as a director (Status: Jan 1996).
• Jason plays ice hockey, for example in an NHL Celebrity All-Star Game on December 3rd, 1995 in San Jose and on January 20th, 1996 in Boston. He practiced wrestling in a club called "Slammers."  He became a co-partner of a company which produces TV movies and videos for World Championship Wrestling (2000).
• Jason was co-executive producer for the video WCW/NWO Superstar Series: Diamond Dallas Page - Feel the Bang! (1998) and for TV movies "First Daughter" (1999) and Shutterspeed (2000) and First Target (2000) and First Shot (2002).
• In March 1993, a former Wonder Years wardrobe assistant filed a sexual-harassment suit against Hervey and Fred Savage. The suit was dropped nine months later. See article.
• He filed lawsuit against Las Vegas wedding chapel for selling his wedding pictures to a tabloid (October 2000).
• Jason has given his voice to a Sega Saturn game called Return to Zork.
• Jason is very different from the character Wayne. "To play a character so unlikable and unsympathetic, you must be funny," Marlens says, one of the creators of The Wonder Years.
• There is an article about Jason Hervey.
• Gossip which is NOT true (thanks to Daniel): 
• Jason Hervey said: "My godfather is [famed wrestling villain] Terry Funk. He once kicked in my pinkie finger. I'm going to be a professional wrestler or manager, I think." 
• In March 1996, Jason Hervey founded the company Interplay Pictures together with Mediaplay.

• The following contact address is NOT valid anymore:

Jason Hervey 
1280 Sunset Plaza Drive 
Los Angeles, CA 90069