I wonder if the transformers_cybertron tag belongs here. Yeah, Cybertron was the only series where we actually saw Primus in his robot mode, and it was confirmed that his alternate mode was indeed planet Cybertron itself... BUT, this doesn't look anything like his Cybertron robot mode. I mean, some of the details are the same, but the colors alone are wildly different.
I mean, compare Primus here to his actual Cybertron toy:
http://2.bp.blogspot.com/-07CZMv4OGCs/TkXoJynubWI/AAAAAAAAOfY/7tMuTL5SeNI/s1600/DSC06328-1.jpg
Meanwhile, Unicron is, aside from a couple colors, an absolute dead ringer for his Armada incarnation.

AntagonistChan said:

I wonder if the transformers_cybertron tag belongs here. Yeah, Cybertron was the only series where we actually saw Primus in his robot mode, and it was confirmed that his alternate mode was indeed planet Cybertron itself... BUT, this doesn't look anything like his Cybertron robot mode. I mean, some of the details are the same, but the colors alone are wildly different.
I mean, compare Primus here to his actual Cybertron toy:
http://2.bp.blogspot.com/-07CZMv4OGCs/TkXoJynubWI/AAAAAAAAOfY/7tMuTL5SeNI/s1600/DSC06328-1.jpg
Meanwhile, Unicron is, aside from a couple colors, an absolute dead ringer for his Armada incarnation.

I think this is more in design with his other robot mode thats featured on the TF wiki