Key

"I did find out this is definitely a key, and I'm pretty sure the Tazelwurm gave it to me. Hmm. What other secrets does this key hold?"

- Lee Ping ("Welcome To Factory Island") The Key is a golden, octagonal shaped key which opens most of the doors in the underground laboratories of A Nigma High and some doors of the Green Apple Splat factory.

History
There are two keys existing and they are the major instruments needed to access the Antiquis Triangulum located underneath A Nigma High.

The Red Tazelwurm placed one of the keys to Lee Ping's bag, sowing it to a secret pocket there ("15th Graders"/"Welcome to Factory Island"). So, the key was in Lee's exposure for the majority of seasons 1 and 2, helping him to open the doors of the underground tunnels.

The key proved to be more important in season 3 when The Council actively tried to get the hold of the both keys, having only one of them in exposure. In "Bed Bugged", after finding out the location of the key, Li 'The Serpent" Ping is sent by the Council to steal it, and the latter keeps the key through the rest of season 3. As of "Follow that Finnwich", Lee obtains both keys. In "Game of Clones" Lee gives one of the keys to his friend Holger as a sign of trust, after which Holger passes the key to Camillio Martinez. One of the principal Wurst clones hunts down Camillio, taking the key away. The Council is once again at hold of both artifacts.

Trivia

 * It is widely believed that the Red Tazelwurm is responsible for putting the key into Lee's bag.
 * This is later confirmed when it's revealed that the Tazelwurm stole the key from the The Council.
 * A common error with the Key is that it always seems to change sizes at random. Normally, the Key is shown to be able to fit into Lee's palm, but once placed inside one of it's special keyholes, it takes Lee two hands to turn the larger key.
 * The important entrance which the key can open includes the door behind A. Nigma High's back of library entrance, where the keyhole is located behind one of the books entitled "The History of Alexander Nigma" where it reveals an octagonal shaped keyhole and once the key unlocks it, the walls on the back of the library open revealing the secret entrance to the underground tunnels leading to A.Nigma High's research labs.