I found it kind of weird that he showed anger at the end at OS/X copying his font, when he had just admitted that much of his inspiration came from comic books. Is this not the pot calling the kettle black?
Maybe I'm focusing on minor details, but Arial has never seemed like a dead ringer for Helvetica to me. Or at least no more than, say, Franklin Gothic and Helvetica are the same font. There are some clear differences in letterforms that give the fonts a somewhat different feel, at least to me.
Having said that, regardless of the differences in execution, it wouldn't surprise me to learn that some Product Manager at Microsoft said "Make me something that looks like Helvetica", and the result was Arial.
I love the irony that Comic Sans was born because the designer was shocked at seeing another font used inappropriately.