Mecha Sonic and Mechagodzilla

Sonic the Hedgehog 2 had its fair share of homages - Super Sonic was inspired by Dragon Ball's Super Saiyan and the Death Egg was inspired by Star Wars' Death Star. But a less obvious one is that Mecha Sonic seems to have been inspired by Mechagodzilla.

It only really becomes apparent when looking at the concept art.

Mecha Sonic:

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Mechagodzilla:

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There are several similarities - the way the arms and legs are connected to the torso by what is essentially corrugated tubing, the indents on the back of the hands, the MS / MG emblems on the upper arms, the rivets everywhere, and of course the colour scheme and "Mecha" name.

There are a bunch of (mostly unused) attacks brainstormed in the concept art, the first two being "lasers from eyes" and "finger missile from fingers" - both signature attacks of Mechagodzilla. Mechagodzilla also has rocket feet just like Mecha Sonic.

The Sonic Adventure version of Mecha Sonic loses some of these references (like the "MS" on the arm) but adds even more overt homages.

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New similarities include the spikes on the knees, the segmented tail and the patterened orange/yellow eyes (fun fact: made from car tail lights). But the biggest similarities are the hexagonal and pentagonal panels on the chest and lower torso - they're identical to those seen on the original 1974 Mechagodzilla, even down to the X and V shaped detailing.

Another curious feature of this version of Mecha Sonic is that it has gun barrel style fingers, kind of like Mechagodzilla after firing its finger missiles.

As for the Sonic & Knuckles version of Mecha Sonic? I don't really know. A new, sleeker version of Mechagodzilla was introduced in 1993, but there don't seem to be any direct parallels design-wise. But this Mecha Sonic does have a red orb when he opens his chest panel, which he uses to fire energy balls - similar to how the original Mechagodzilla has a red orb behind its chest panel that fires a "Cross Attack Beam".