So I was looking at some early 2000s items I have and I realized that as far back as Spy Troops (at least on the packaging) that the core group for GI Joe has been roughly the same 5 characters:
Duke, Scarlett, Snake Eyes, Tunnel Rat and Heavy Duty/Roadblock.
Granted this does not hold in the comic universes, Resolute or ROC, but Spy Troops, Sigma Six (mostly) and currently Renegades all follow the same formula of this small core group and "adding on" as they go.
So why these 5? I get Duke and Snake Eyes, because they have to be in every incarnation of the brand. Just as Optimus Prime and Bumblebee have to be in Transformers. Scarlett is the defacto female, but could be replaced. Roadblock/Heavy Duty is the default "big guy" with ethnicity, but why Tunnel Rat? When did he become popular?
I just wonder when, and why, these 5 characters seemed to be selected by the higher-ups as the core team?