Repair work would be going much faster if our forces weren't split between the Death Egg and that frivolous amusement park of yours!
I told you! Carnival Night is tactically important!
— Dr. Snively and Dr. Eggman, Sonic the Hedgehog #290
Construction on the carnival, alongside the Death Egg's repair work, was overseen by Dr. Eggman's assistant Dr. Snively while his boss was away working on other schemes. The carnival's construction made the Death Egg's repairs considerably slower as forces were spread between the two, but Eggman insisted the Zone was "tactically important".
Sonic the Hedgehog 3 & Knuckles
After Sonic the Hedgehog made Dr. Eggman's Death Egg crash land on Angel Island, he and Miles "Tails" Prower passed through Carnival Night Zone during their mission to destroy the flying fortress for good. Knuckles the Echidna later passed through Carnival Night Zone in pursuit of a fleeing Eggbot controlled by Dr. Snively after multiple encounters on the island.
Team Dark and a Tele-Pod controlled by Snively passed through Carnival Night Zone after landing on Angel Island in an attempt to reach and secure the Master Emerald before Eclipse the Darkling. While passing through this Zone, Omega blew up a barrel.