Charles Schulz Interview 1985
Charles Schulz and actress daughter Jill on a local morning talk show promoting the premiere of the CBS special IT'S FLASHBEAGLE, CHARLIE BROWN. About a minute in, Jill becomes the focus. She was the animators' model for Peppermint Patty's aerobics dance in the special. Then the audience asks more questions to Mr. Schulz. There is a funny confession in the last minute of snippet.
Since Flashbeagle originally aired April 16, 1984, this was probably aired prior to that date, but the YouTube poster put the date at 1985.