The Cosmic Interstate (also known as the Cosmic Highway or Interdimensional Highway) is a series of pathways connecting the various Zones and parallel universes of the Multiverse that Sonic the Hedgehog and his friends often end up in. Accessible through a number of methods, it has been used by Sonic and others on a number of occasions. It is patrolled by the Zone Cops of the No Zone under the leadership of Zonic, and was once devastated by an attack from Mammoth Mogul before being restored by Titan Tails. Later, it was placed under heavy lockdown as the Zone Cops became embroiled in a war with the evil Dr. Nega, who has used the highway to wreck chaos in the zones. This led the interstate to be badly damaged and heavily patrolled to prevent unauthorized travel between Zones.
Sonic's First Journey
Sonic first used the Cosmic Interstate when he attempted to use it as a shortcut to quickly get to the other side of Mobius and shut down a factory that Dr. Robotnik was using to pollute a river. By accident, he wound up on Anti-Mobius instead, and met his counterpart Evil Sonic for the first time, sparking a rivalry that would continue for years. After his first defeat of Evil Sonic, Sonic made his way back home through the interstate. (StH: #11)
Night of 1000 Sonics
A cybernetic version of Sonic travelled the Interstate to Mobius Prime to search for allies against Robo-Robotnik, who planned on taking over the multiverse. Sonic traveled the Interstate to recruit multiple versions of himself to stop Robo-Robotnik. Teaming up with Robotnik Prime, Sonic Prime led a group of alternate Sonics to an area of the Interstate containing the powerful weapon, Giant Borg. However, Evil Sonic, recruited by Robo-Robotnik distracted the other Sonics long enough for Robo-Robotnik to steal Giant Borg. After the multiple Sonics spin-dashed Giant Borg and Robo-Robotnik to pieces, each of the alternate Sonics took a piece of Giant Borg back to their home zone to prevent reassembly. (StH: #19)
The Anti-Freedom Fighters/Suppression Squad
The Anti-Freedom Fighters would later become bored and decide to make their good counterparts look bad by impersonating them and causing mischief on Mobius Prime. They were, however, defeated by the Freedom Fighters and sent back home. Unaccompanied by the rest of his gang, Evil Sonic would then bring Anti-Knuckles through to Mobius Prime to help him steal the Angel Island Chaos Emeralds. Despite teaming up with Dr. Robotnik, Evil Sonic would be defeated by the Knothole Freedom Fighters and Anti-Knuckles. Evil Sonic would later violate the Cosmic Interstate on other occasions, namely: joining up with Robo-Robotnik to gather the pieces of Giant Borg, only to deliver them to the Sonic Underground version of Dr. Robotnik; vandalizing the world of Litigopolis; knocking out Zonic the Zone Cop and escaping to Mobius Prime; and switching himself and Anti-Freedom Fighter Patch with their Mobius Prime versions. Patch was later returned to his home Zone, while Evil Sonic remained on Mobius and became Scourge the Hedgehog. (StH: #24, #44, #112, #150, #153, #156; SSS: #10, #14)
Following his own return to Moebius, Scourge would reorganize the Anti-Freedom Fighters into the Suppression Squad and bring them back to Mobius Prime. They remained there for some time, clashing with the Freedom Fighters until returning to Moebius after the Suppression Squad rebelled against Scourge. Prior to that, Sonic and Amy Rose traveled to Moebius in hopes of finding allies against Scourge. (StH: #188, #189, #190, #191, #192, #193, #194, #195)
Mammoth Mogul's Rampage
After absorbing a vast amount of power from Chaos Knuckles, Master Mogul would rampage across the Cosmic Interstate. Destroying numerous Zones, he would later come against the No Zone itself before being defeated by Titan Tails, who also restored all the destroy Zones to normal. (StH: #149, #150)
After defeating Scourge on Moebius, Sonic carried his unconscious body through the damaged Interstate to the No Zone. Scourge awakened and the two hedgehogs briefly fought until they were arrested by Zone Cops Zespio and Zector for violating a zone lockdown. They were taken to the No Zone where it became a war zone, which the Zone Cops were then forced to chase Scourge through as he escaped. During the pursuit of Scourge, Zonic told Sonic that the Cosmic Interstate travel was off limits because numerous zones were struck by a fiend Sonic previously encountered, Dr. Nega. Zonic also explained some Zones were allowed to remain open due to keeping the multiverse balanced. After Scourge was captured and questions about Dr. Eggman were answered, Sonic returned to Mobius Prime. (StH: #196, #197 SU: #1)
The Destructix later took on a job for Dr. Finitevus, who gave the team access to the Cosmic Interstate. Focusing on her original plan to break Scourge out of Zone Jail, Fiona, along with the rest of the team, planned to get captured by the Zone Cops and sent to the same prison as Scourge. When they were confronted by Zone Cops for violating the zone lock-down, they reacted with extreme violence, destroying a number of squad cars while seriously wounding several officers. When they succeed in breaking Scourge and themselves out of Zone Jail, they no longer had a need for the Cosmic Interstate, and they again used one of Dr. Finitevus' Warp Rings and returned to Moebius. (SU: #29, #32)
- The Interstate seems to be part of, or is inside of, the Neutral Zone.
- The atmosphere and even the roads of the Cosmic Highway vary, as once it was shown as an highway with a normal sky in #197, but has a green translucent road with a dreamlike sky in Sonic Universe #1.
- Since the multiverse collapsed upon and rebooted itself due to the Super Genesis Wave's improper reversal, the Cosmic Interstate presumably no longer exists. Ian Flynn has confirmed that Mobius Prime and the Sol Zone are among the handful of interdimensional realities not completely destroyed as of the end of Worlds Collide. [http://www.bumbleking.com/forum/viewtopic.php?f=4&t=7879&sid=9448d408e875665fc0e617717ee61cb0&start=105)