"Lover Boy" gives Ken Curtis a chance to show what a good actor he is. Shorn of facial hair, he plays a charming and heartless rogue who loves 'em and leaves 'em. (In real life, he would have seduced the women, but this is only vaguely suggested by his first conquest being sufficiently humiliated that she becomes a saloon girl.) Curtis shows how good he is at creating characters almost entirely by facial expression.
Consider John Anderson, Royal Dano, and Morgan Woodward, veterans of many TV Westerns. With few exceptions, each is instantly recognizable. Not Ken Curtis. You'd have to think a while before recognizing Curtis as both Kyle Kelly and the original Festus. (The latter Festus is even more distantly removed.)
Curtis started out as a conventionally handsome man, with vapid good looks. (It's easy to see why John Ford's daughter was so hot for him.) He got better looking as he matured and his features grew more angular. In an unintentional bit of humor, one of his conquests complains that her husband is "nearly 50". * So was Curtis -- he was 48 when this episode was shot! ** He was nearly 60 when the series ended.
Though Festus and Chester were "similar" characters, Festus had the athleticism Chester lacked. *** In fight scenes, Curtis is quick and nimble -- you wouldn't want to get on his bad side. And in an early Festus episode, when he and Slim Pickens are about to be strung up in a stable, Curtis leaps up off his horse and wraps his legs around the beam.
An above-average episode -- strongly recommended.
* 50 was considered "old" in the 19th century -- retirement age, essentially.
** In "Lover Boy", he looks closer to 60 (or even older). Strange as it might seem, the Festus whiskers shave a good decade off his apparent age.
*** Dennis Weaver supposedly suggested Chester have a stiff leg, as he didn't find it plausible that an able-bodied young man would take a poorly paid job as the marshal's assistant.