Aside from his co-hosting duties, it also fell upon McMahon during the early years of Carson's tenure (when the show ran 105 minutes) to host the first fifteen minutes of "Tonight", which did not air nationally. McMahon also served as guest host on at least one occasion, substituting for Carson during a week of programs that aired between July 29 and August 2, 1963, and again for two nights in October 1963. McMahon served as a counter to the notoriously shy Carson. Nonetheless, McMahon once told an interviewer that after his many decades as an emcee, he would still get "butterflies" in his stomach every time he would walk onto a stage and would use that nervousness as a source of energy.