|This character exists primarily or exclusively within the Sonic Underground continuity.|
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
- For other versions of Robotnik, see Robotnik (disambiguation).
Good Robotnik is essentially a doppelganger of his Mobius counterpart. Physically, the two of them are identical, except that Good Robotnik has a brown mohawk-like hair. He also wears the same attire as his counterpart, although his is slightly torn up.
On an alternate Mobius where the Sonic Underground (Sonic, Sonia and Manic) are the evil rulers, Robotnik is the leader of the Resistance trying to take back the kingdom for the good of the people. At first, the "real" Sonic the Hedgehog obviously confused the good Robotnik for the real "bad" one, and made critical remarks of him. After a while, however, Sonic and the good Robotnik teamed up to defeat the Corrupt Hedgehog regime.
After capturing the corrupt hedgehogs, Good Robotnik showed the tyrants the misery their rule had caused the common people. After the Hedgehog rulers had a chance and vowed to right their wrongs, Good Robotnik stood by them to rebuild the Kingdom. 
Good Robotnik is very nice and congenial to the other Hedgehogs' good counterparts. Sonic Underground in turn showed the same respect back, though Sonic did once refer to him as "Robuttnik" by mistake, admitting it was a tough habit to break.
Robotnik says he knew the royal hedgehogs when they children back when they enjoyed music. He is also willing to give the siblings a second chance to redeem themselves.