The Big O

[TheBigOFan72]

Seriously, it's so much different from all the other megadeuses. Why does Big Fau have to have that long head?

[yellowc]

idk but i know his head is long as my **grok** lol

[g2kmaster]

I think it is something related to Japanese onmyoji (Ying Yang Masters). They were pretty powerful people - casting spells, watching the constellations for omens, and a lot of other stuff.  The creators may have seen it has trying to show Fau is the more powerful megadeus seeing that he is hyped by Alex to be the be-all-end-all megadeuse but doesn't see Big-O pull something awesome out of his ass one last time and blow him away pretty much till Big Venus raises the roof.

[Kobun20]

"To be distinctive" seems like a good answer. Sometimes I think the top of his head resembles a submarine (from the front) or a marine mammal (more from the side) so maybe it ties into his underwater supremacy too.

[nslay]

You could generalize this question to: Why are all the robots humanoid or the form of some animal?

I think the optimal fighting robot may not actually be humanoid in shape. Are jet fighters the shape of predatory birds?

Their appearance seems to be the artist's choice and may very well not serve any functional purpose (e.g. robots don't need a face like Big O/Duo/Fau).