To catch that annoying blue hedgehog, you must become the annoying blue hedgehog.
This mod replaces Sonic's model with Dr. Eggman's in Sonic Adventure 2. The initial mod was built before full-on model editing was made manageable for SA2, and as such, it's designed using the game's assets and model structures first and foremost. A "Shadow Eggman" is also included to act as the Dark counterpart to Speedy Eggman, which was made possible with said advancements in model editing techniques.
Simply replacing Sonic's model in this game with Eggman's was normally not possible due to the two having entirely different node structures. In order to accomplish this, Eggman's model needed to be adjusted in several areas to accommodate Sonic's set animations, but also not to a degree where his in-game model would be severely compromised. As the mod was created before proper editing tools could be made, several of these changes needed to be done by hand.
Credit to x_ander_519 for the Night Sky Rail texture mod seen in the title image.