If there was ever any doubt in my mind that Rex Allen was using material originally meant for Roy Rogers it was settled in this film. Allen's horse Koko takes center stage here and with Mary Allen Kay as his ersatz Dale Evans leading lady, no way this was not meant for Roy.
Rex and Koko together with sidekick Buddy Ebsen are hired by Tris Coffin who is running half of a wild west show. Rex is taking the place of Coffin's former partner Buff Brady who was killed while trying a jump on a Roman style team of horses. What no one knows is that fellow rodeo performer Roy Barcroft sabotaged the harness with a little acid. And Coffin accepts him as a silent partner.
Ironically Roy Barcroft who usually plays crafty villains in a Gazillion westerns is really a rather stupid and jealous man here. Coffin might never have even been suspected of villainy on his own had he been able to put a muzzle on Barcroft. But Barcroft was jealous of Brady and now he's jealous of Allen and his horse Koko.
Also wanting Koko is Brady's daughter Bonnie DeSimone who is about 10 years old and has inherited her father's end of the partnership. Coffin though is cheating her out of her end of things.
Mary Ellen Kay who was being groomed as another Dale Evans by Republic Pictures Herbert J. Yates is DeSimone's guardian. She and Rex make some beautiful music singing and not singing. And the little girl falls in love with Koko after Barcroft injures him and she nurses him back to health. Rex almost gives him up and I can't Roy Rogers doing that with Trigger under any circumstances.
Rodeo King And The Seniorita is a pleasant enough Rex Allen western. But I also can't figure out why no investigation into Brady's death was done as a matter of routine.