An important figure in network TV during the 1980s and 90s who rose to prominence at NBC during its lengthy hold on the Number 1 spot in primetime ratings. Spotted by NBC president and wunderkind Brandon Tartikoff after he co-produced a TV-movie for CBS, "The Last Giraffe" (1979), Littlefield quickly rose through the ranks at NBC via its comedy division, developing such signature hit series as "Cheers", "The Cosby Show", and "The Golden Girls".

In positions as senior and executive vice president, Littlefield was second among program executives to Tartikoff alone and became known as his heir apparent. Despite a rocky working relationship which included a lot of what Littlefield has termed "respectful fighting" in which his judgment was sometimes questioned by his superior, Tartikoff and Littlefield enjoyed a singularly productive tenure at NBC together. After Tartikoff gradually severed his tie with the slipping NBC in the early 90s to became chair of Paramount, the even-keeled Littlefield stepped into his high-pressure shoes, declaring his interest in promoting fictional drama series as NBC's mainstay rather than relying on an excess of sitcoms, reality-based programming or TV movies. Under Littlefield, the network enjoyed a long run as the Number One network but as decade drew to a close, NBC's ratings share began to dip. Just shy of his 20th anniversary with the network, Littlefield stepped down and entered into a non-exclusive program development deal with his former employer.

In 1999, he formed Littlefield Co., a TV production firm that focused on broadcast properties that also could be exploited on the Internet.