Barbary Coast

The plots had a similar complexity to the wonderful Robert Conrad/Ross Martin series Wild Wild West, and the characters are rather similar, though their attributes were combined and scrambled into the two new characters. Here Shatner is the disguise master, but is also the nominal lead, while disguse-master Martin played second fiddle to Conrad 10 years earlier.

Unfortunately, the intelligence (or rather, attention) of the audience had so deteriorated over the previous decade that this show was promptly canceled because the plots were deemed too complex.

If you've never seen Wild Wild West, see that instead. If you've seen that already and you're willing to put up with Shatner, then this can scratch your itch.