James Earl Jones (b. 1931) is an actor noted for his work on stage, film, and television, including the plays The Great White Hope and Fences; films such as Dr. Strangelove, Field of Dreams, and Patriot Games; and providing the voice of Darth Vader in the Star Wars series.
Jones, who had studied acting with Will Lee (Mr. Hooper), is considered by Sesame Workshop to be the first celebrity guest on Sesame Street,  since inserts of the actor reciting the alphabet and counting numbers appeared in the unbroadcast test pilots and heavily influenced the show's pedagogical models. These inserts were later included in first season episodes, beginning with episode 0002. However, Jones didn't originally think the show would last and thought the Muppets were the problem; he told Matt Robinson that "this Muppet business has got to go, kids will be terrified."
In 1979, Jones hosted the Sesame Street 10th anniversary special, titled A Walking Tour of Sesame Street.
The James Earl Jones Factor
CTW consultant Gerald S. Lesser and other researchers paid particularly close attention to James Earl Jones' appearance, in terms of children's response and the effectiveness of his alphabet recitation. Lesser described the basic performance as follows:
During the recitation, each letter appeared briefly near the actor's head prior to its being named, remains for the recitation and then disappears, and a pause in both Jones' speech and the visuals occurs before the next letter. The result of this particular staging prompted a particular positive response from viewers that producer Samuel Y. Gibbon, Jr. and research director Edward L. Palmer, as well as Dr. Lesser, termed "the James Earl Jones effect." The first time a child sees the performance, he responds to the invitation to say the alphabet along with the actor. Upon later viewings, the children would name the letter as soon as it appeared, but before it was named by Jones. Further repetition encouraged children to shout out the letter even before it appears. The "James Earl Jones effect" thus demonstrated to Sesame Street's producers and curriculum advisors the value of both repetition and anticipation, and supplied proof that Sesame Street could promote interactive learning as opposed to merely passive viewing.