Only the voice of Ted Cassidy (Lurch) as Frankenstein Jr gives this any interest nowadays.
The late Mr Halliwell in his TV Companion described this as "witless". He's right - there's nothing to hold the attention of an adult. There are also large credibility gaps. Case in point: the Impossibles are fighting "Billy the Kidder" who attacks the boys with a cannon that appears from absolutely nowhere out in the desert. Definitely one of Hanna Barbera's lesser efforts (sad to say as it was a favorite of this writer and some of his companions at the time)Maybe worth a look for nostalgia purposes otherwise give it a miss.