While there, he is infused with laughing gas and left by the dentist due to emergency reasons, wherein a plastic blowfish almost chokes his numb mouth.
The chasm is filled with gas fumes (a mixture of helium and laughing gas, causing anyone who breathes in it to laugh uncontrollably while speaking in a high-pitched voice).
This experimental procedure nearly proved fatal on several occasions, but led to the discovery of the unusual effects of nitrous oxide, which came to be known as laughing gas.