My question relates to what is "size"?
Can Galactus Pilot The Bug because they both have the same sized Base, or, can The Bug only be piloted by a Giant or smaller, because the Bug has a Giant symbol on his base, which grants him the Great Size ability. (Not to be confused with Tiny Size which is granted by the Tiny symbol.)

Character size information can be found on the PAC above the DAMAGE powers section.

It states:

Thank you. I had missed that.

Just in case there's any confusion. 6x3 is not the character's "Size" in Heroclix. The characters size is or or or .

So to be clear...size does matter.

Right, but until that part was pointed out to me, I couldn't find a reference to "Size" in the rule book or players guide. Didn't even think to look at the PAC.
Might be something to add to the Glossary in the rule book.

From the Player's Guide:

As indicated on the Powers and Abilities Card, smaller characters do not block the line of fire to or from larger characters.

so no colossals can be a pilot? Cause wasn't it put on the watchlist that colossals cant be pilots already?

Not at this time.

just wait until the beyonder comes out where he can shink down to human size

Now to play munchkin here.

Colossal figure gains Earthbound (Through use of Infinity Gauntlet or some other power that lets figures choose a power)

Can he then Pilot the vehicle?

I would think not as the EB would be ignored.

I meant the definition of size from my original post.

Why would it be ignored?

Woah woah woah, wait just a second.

Since when did giants stop blocking LOF between colossals?

I was definitely under the impression that both a giant and a colossal are on elevation [insert large number of choice here], and block LOF to others who are either giant or colossal.