The Three Musketeers (American TV series)

The Three Musketeers is an American Saturday morning cartoon produced by Hanna-Barbera Productions for NBC. It premiered in 1968, running for 18 episodes as a segment on "The Banana Splits Adventure Hour". The cartoon is based on the famous 1844 novel "The Three Musketeers" by Alexandre Dumas.
Premise.
Athos (voiced by Jonathan Harris), Porthos (voiced by Barney Phillips), Aramis (voiced by Don Messick), and D'Artagnan (voiced by Bruce Watson) partake in new adventures fighting the enemies of the crowned heads of France King Louis XIV (voiced by Don Messick) and Queen Anne (voiced by Julie Bennett). They are sometimes assisted by a queen's handmaid named Lady Constance Bonacieux (voiced by Julie Bennett) and her young nephew Tooly (voiced by Teddy Eccles). A recurring theme has Tooly trying to prove himself worthy of becoming a Musketeer but the Musketeers won't allow him into their services because of his age. Tooley, who has a white horse, named Lightning, does get a present from the Musketeers, a mule for his birthday. Several of the cartoons end with the famous "All for one, and one for all" slogan.