Artwork and aesthetics:
I've never been one to pay much attention to the art of a DM card (MtG cards, on the other hand...), especially since nobody pays attention to my dream cards because they don't have art! But I might as well try to emulate Nerafim and talk about it.
Cyber G Hogan is a muscular Cyber Command. That prominent dark circle on the left of its art is a fist, which you can take to represent its powerful impact on the game state. Connected to that fist is a...chain. It's pretty obvious what that chain represents. Now you can't see G Hogan's other arm, but if it were like the arm shown on the picture, you would have two chains. A double chain, which is exactly what Chain Cascade is.
Despite it being a card released in the later sets, its body structure isn't as convoluted and confusing as, say, Romanoff Kaiser NEX. You can see a navy-skinned humanoid creature with a prominent arm.
Now to discuss its race and civilization. Water is known for playing creatures from the top of the deck, dating as far back as Transmogrify and appearing occasionally, like in the form of Emperor Chirico and Hellrush Max. Chain was one of the 6 main Soul mechanics in the psychic set block, and it corresponded to Magic Soul. You can say Cyber G Hogan is the boss of the Magic Soul creatures/Chain creatures (a sentiment further supported by Deepsea Resist's flavor text and his appearance in DM-39 as G Hogan, Temporal Star / Ocean G Hogan, the Best Awakened). Cyber Commands have been used as the boss creatures of the Water civilization ever since their introduction in DM-32, like Twilight Sigma, Maxwell Z, and Cyber A Irons. (Speaking of Cyber A Irons, it has a smiley in Japan: ・A ・, which comes from its name. Seriously, just look at the name section of a picture of the card and tell me you don't see a smiley.)
When Cyber G Hogan comes into play, look at the top 2 cards of your deck, and you may put any number of creatures that cost less the G Hogan into the battle zone.
2! 2 creatures! Ha ha ha!
As always, effects that put creatures into the battle zone for no cost are very powerful, as evidenced by the cards Soulswap and Transmogrify, as well as a horde of other powerful cards. Putting cards into play for no cost has been a powerful strategy for a very long time, and Cyber G Hogan is just one of those powerful ways. Being an 8-cost Cyber race card that summons multiple creatures make it reminiscent of Emperor Chirico, which ruled the metagame during DM-32 to DM-35 before being restricted.
Now for stuff specifically about G Hogan. Playing 2 creatures is always good, even if the creatures themselves aren't that great, because you get 3 creatures into the battle zone for the price of one! And if you filled a deck with several creatures with powerful comes-into-play effects, Cyber G Hogan would really shine!
The main way to use Cyber G Hogan is in a water/darkness/nature control deck made up entirely or almost entirely made of creatures. The deck would start by using Bronze-Arm Tribe and Jasmine, Mist Faerie (Faerie Life is a no-no, since this deck has to be nearly completely creatures), and later summoning Cyber G Hogan to play creatures such as:
■ Olzekia, General of Decapitation, for powerful removal
■ Jenny, the Dismantling Puppet, for discard
■ Magical Dragon Babelginus, to put Cyber G Hogan into play again to play even more creatures (and I've experienced it enough times to tell you how ridiculous that can become)
■ Cyber N World, for hand replenishment
Fire can be splashed into the deck for Kiryu Jilves, Gaia's Roar and Blazing Tiger, Crimson Lord. Bolshack Superhero, a card that's been recently released in Japan, is another creature with comes-into-play effect that G Hogan can put into the battle zone. Bolbalzak Ex is also excellent in a G Hogan deck, as it untaps all your mana so you can take your hand for another spin!
Here's an example of one of those G Hogan decks.
Cyber G Hogan is often used in TCO in decks based around Twilight Sigma, the Super-Electric. With Sigma, you can play Cyber G Hogan from your hand easily. Cyber G Hogan has also seen use in TCO Chain/Marshall Touch decks, where Marshall Touch would be used to reuse G Hogan.
But none of those are quite as prominent and powerful in Japan as the first, not that I'm ridiculing them.
Combos with other cards:
Vacuum Crawler needs so much more love. Seriously, it lets you draw and reuse powerful comes-into-play abilities...like G Hogan's, of course! It lost a bit of shine during these later sets, but it's still good.
Magical Dragon Babelginus is a way to reuse G Hogan, as mentioned above.
Kiryu Jilves, Gaia's Roar has been a well-known and useful card in Japan for a long time as an instant counterattacker, and it can be used in G Hogan decks as a finisher once you play several creatures with Hogan.
Pulpy Goobie lets you choose what creatures you play with G Hogan, which is very important. You could even set a Babelginus to be summoned with your next G Hogan, and set the creatures that will enter the battle zone when Babelginus reuses Hogan's effect! You could also try to use Aqua Strummer, but Pulpy Goobie is much more useful as a blocker.
Intense Boiling! Hot Spring Gallows lets you double your G Hogan for double the fun If you want to use it, don't use a hyperspatial spell; you should use Raging Apache Lizard. Raging Apache Lizard is useful with Hogan, as it's a creature with a good enters-the-battlefield ability that costs less than Hogan. If you get it with Hogan, you basically get 4 creatures for the price of one.
Speaking of creatures that play psychic creatures, Geo Crashing Miranda, the Dimensional Force is an all-star for the various useful psychic creatures it can get out, like Victorious Meteor Kaiser and Saint Ave Maria, Light Weapon. Cebu Algol, Electro-Vanguard and Gaga Carina, Spirit of Lightstreams only wish they could get out creatures with cost 6 or less instead of 5...
G Hogan, Temporal Star does not combo with Cyber G Hogan. All summoning is putting into the battle zone, but not all putting into the battle zone is summoning. Summoning is a very specific form of putting into the battle zone.
Ways to counteract it:
Magnum, Allshot Puppet, known on TCO as Hundred-Strike Doll Magnum. Just...that. It gets rid of the creatures played by G Hogan, so you don't get to expand your field with them. Of course, you still get the powerful comes-into-play abilities, but the field expansion is very important.
Since you're likely to be putting large amounts of creatures into the battle zone, always beware of Apocalypse Day, lest your field asplode.
Strengths? Haven't I just described them in the previous sections? I may as well repeat them.
For 8 mana, you get an 8000 power double breaker plus several creatures and potentially using powerful comes-into-play effects.
Its only weaknesses are its prominent cost of 8 and its tendency to hit spells instead of creatures in certain decks...but if you're using Cyber G Hogan, you should not be running very much spells at all. Not to mention that cost of 8 is part of what makes its Chain Cascade work so effectively, as if it were 1 lower, it could not play Babelginus, or Olzekia, or Bolbalzak X! If it cost 7, it would be severely missing out on many things.
There are no variations on this card! Its Chain Cascade ability is totally unique to itself! The closest you could possibly get is Cyber T Crown, which only has normal Chain, so it works so much less effectively.
Oh, you were talking about art variations? Well, G Hogan has none of those too.
I'd give this card a 9.5/10. Seriously, the power it packs is absolutely insane, although it's kind of overshadowed by other meta cards.
CAN'T FIGHT THE HOGAN POWAH!