There was nothing between Kat and Jason on Power Rangers. In MMPR, Jason was long gone before Katherine took over as the Pink Ranger. And by the time Jason he returned as the Gold Ranger, Katherine was already infatuated with Tommy, and it didn't take long before Jason found another love interest in Angel Grove: Emily. Still, I honestly think they could've been a great couple! They are both extremely caring individuals, fulfilling the roles of "Protective Brother" or "Compassionate Sister" for just about every other Power Ranger. They were both looked up to as exemplary, accomplished individuals, both for their athletic accomplishments as well as their maturity and determination to succeed. Also, in the episodes revolving around Tommy's disappearance, they were united in their deep worry for the Red Zeo Ranger. If Katherine and Tommy never got together, then I'd bet Jason would've found his soulmate in the Pink Zeo Ranger. And, after reading various fanfics, I'm sure I'm not the only one who sees the incredible potential they carried.