RPM Zord Design
 

I think the reason why Doctor K made the ranger suits with a car motif is maybe a homage to her dad. While the cute animal motif of it might be a homage to her mom. Remember she was taken away as a child and the fond memories of her parents probably was all that she had. Now the reason why I'm saying this is cuz Sheldon Cooper is good at american football cuz of his dad. K parents mightn't have known how to move with her(I'm assuming), but they bonded with her none the less with the only way how. Or you know That could've been alphabet soup's call.

re rpm zords
 

The animal motif came from the Ranger technology itself. Doctor K explained that the Zords were made with animal DNA coding, or something to that effect. That's how she changed Venjix's Doomsday Machine into a whale.

Re: RPM Zord Design
 

In the episode 'Doctor K', she had been inside Alphabet Soup for so long, she forgot her REAL NAME, so its probable she may have forgotten her parents after so many years of being lied too and forced to do science! stuff. The animal motifs could be because she likes cute stuff, and the car theme due to the Rangers needing to be able to get to the monster asap cause they live in a dome.

Re: RPM Zord Design
 

I think the zords were based off of animals since most of the zords.lin the RPMU were probably animal based.