First Ladies who did unpaid TV appearances / non-profit media gigs

 FLOTUS Nancy (Davis) Reagan

appeared on an episode of

Diff'rent Strokes  (1983 season)

as well as

Sesame Street (in 1985).

In both cases she was not

promoting herself but instead

Reading

& 

the "Just Say No" campaign.

_________________________

Mrs. George H.W. Bush (Barbara)

appeared on an episode of

Sesame Street in 1989 (#2660);

Hillary Clinton in 1993 for the

Season 25 premiere episode;

among a list of appearances,

FLOTUS Michelle Obama

appeared in 2009 for the show's

40th Anniversary, talking about

her non-profit "Let's Move" 

initiative on healthy exercise

and eating for kids & youth.