The Mega Mack is a pink liquid with texture seemingly identical to that of water. Its properties are inconsistent though. Western materials refer to Mega Mack as a toxic liquid which can poison Sonic in a manner of minutes, while Japanese sources simply refer to it as water with an odd coloring. Regardless, Tails has been unnerved by Mega Mack, hinting it is indeed an unpleasant substance.
In gameplay, the Mega Mack has the properties of water (apart from its color), meaning that the playable characters can drown after being submerged in it for extended periods of time. Contrary to western descriptions though, the playable characters will suffer no form of poisoning from being submerged in Mega Mack.
In gameplay, the Mega Mack has no air bubbles in it, so it is easier to drown in. Also, the Chemical Plant Zone boss, Water Eggman, uses Mega Mack as part of his attack pattern. He will fill up his canister with Mega Mack and attempt to dump it on Sonic or Tails. Additionally, the rotating platforms that the battle takes place on will dump the player into the Mega Mack, which will result in an instant death.
In the Sonic the Hedgehog television series, the Mega Mack is referred to as Mega Muck. Also, instead of being a poisonous liquid, it is a glutinous substance which is used to impede Sonic the Hedgehog's movements, similar to super glue.
The second scientist who worked with Robotnik to invent the Mega Mack was caught in a chamber that flooded with Mega Mack, but instead of dying he was transformed into the villain Megatox, whose body is made up entirely of the substance.
In the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics, the Mega Mack is referred to as Mega Muck. Originally, it seemingly had the same properties as the Mega Muck in the Sonic the Hedgehog television. However, its later appearances would depict it as a toxic chemical, like in the games.
After the events of Worlds Collide, the Mega Mack is now seemingly identical to its game counterpart.
Early Sonic canon
Early on in the Sonic series, Mega Mack, also referred to as megamalatricarboSonichloride, was discovered by chance when Dr. Robotnik was fiddling around with chemicals to employ against Sonic, which he marketed as "Mega Mack." The substance was described as extremely lethal, turning anything submerged in it magenta before killing it in less than a minute. However, it was also highly corrosive, disintegrating the barrels for storing it in a few hours. This gave Robotnik the idea of using the Mega Mack to flood the Chemical Plant Zone when Sonic would arrive.
↑Sonic Team (4 November 2011). Sonic Generations. PlayStation 3. Sega. Area/Level: Chemical Plant. "Miles "Tails" Prower: This Chemical Plant feels familiar. I'd never forget a smell like this! And that pink water makes me really nervous for some reason."