Inasmuch as Atom Ant was a satire on superheroes, falling more toward Mighty Mouse than Superman, Secret Squirrel mined the same comic vein as the live-action Get Smart, sending up the secret agent genre that was hot at the time thanks to the James Bond movies.
Fabricio Jiminez uploaded the open:
To most observers, you'd think Secret Squirrel was mostly a showcase for two of the most well known and respected voice actors in the business--Mel Blanc (Secret) and Paul Frees (Morocco Mole, the Chief, others). In fact, Frees uses the same voice mannerisms for the Chief that he'd previously created for Inspector Fenwick in the Dudley Do-Right shorts for Jay Ward. Frees also was the man behind Secret's #1 nemesis, Yellow Pinkie, who, although a parody of "Goldfinger", had more in common with another Bond foe, Blofeld, with his recurring appearances.
When Hanna-Barbera decided to revive Secret Squirrel as the backup feature to 2 Stupid Dogs in 1993, they decided to repopulate the supporting cast with animals, turning the Chief into a yak, for example. I don't know about you, but nothing beats the original.