In answer to CBS' long-running In the News, NBC began a series of PSA's featuring stars from several of their prime-time series in 1983. One to Grow On aired several times every Saturday morning from 1983-89, before the network decided to replace it with something similar.
Stagermonkey uploaded this example, featuring Joel Higgins (Silver Spoons), to YouTube:
Other stars included The A-Team's Dwight Schultz & Mr. T, the latter of whom also had his own cartoon at the time, Rene Enriquez (Hill Street Blues), Soleil Moon Frye (Punky Brewster), David Hasselhoff (Knight Rider), & Michael J. Fox (Family Ties). Today, NBC could revive the concept and mix it with its current Qubo package, but it isn't, and that's a shame. Today's kids could learn the same lessons.