An antenna since he's meant to be a robot
Didn't bombermen originate in Lode Runner? They were robots in that, so yeah it's probably an antenna. I don't know if Bomberman series bombermen are still robots or just humans wearing helmets.
NES bomberman and NES lode runner port are connected
japanese version plays it straight
the design of lode runner enemy sticked, the rest of this "canon" was trashed
i don't think bomberman was a human at any point of the series
it makes him look like a seedling, perhaps their race reproduces like plants do, not sure why they're good with bombs maybe they needed ground to spread so they developed bombs to open up new areas and clear rocks and things
always thought it was a samurai type thing