LOS ANGELES—The NBC action-comedy Chuck, familiar to millions of viewers from its long-running promo bumpers, does not actually exist, network executives admitted Friday. "We had a very successful, very expensive promotional campaign, but to be honest, we never actually bothered making a pilot," NBC spokesperson Grant Twombly said. "I guess everybody just assumes everybody else is watching it, because advertisers have jumped on board, and DVD sales are somehow doing great." A ratings analyst reached for comment confirmed that "people can't get enough of that Chuck."