I'd say Morton is my second favorite Koopaling, and he was, until Iggy's new design surfaced on New Super Mario Bros. Wii. He still remains high though and I think it's because he has such a drastically different look from the others. The dark coloration makes him stand out, but really... I just love the star on his face. I like stars... a lot. That's why I have a tattoo of one (well that and to cosplay Black*Star from Soul Eater... man I've referred to Soul Eater a lot here!)

I've always assumed Morton was named after his grandfather, I mean where else did that Jr. come from in his name. I've always theorized that Koopas have extremely tenacious, recessive genes. If even a single Koopa in their blood line looked a certain way, it's possible for those traits to resurface. I figure that Bowser's father, Morton Sr., had the exact same coloration as Morton Jr., so he was named after his late grandfather (yes, I know that officially they're not related to Bowser, but that's my theory and I'm sticking to it XD)

I also picture him with the voice of Storm the Albatross from Sonic Riders. So there's that