Oxy-Chew is a type of taffy invented by Gyro Gearloose.
Oxy-Chew, a blue taffy substance with the flavour of oxygen, allows the user to breathe in an oxygen-less area after they've taken "five good chews" of it. It was invented by Gyro, and used by him, Fenton Crackshell, and Scrooge McDuck while exploring the Moon in search of the fabled Green Cheese of Longevity. Gyro felt, in addition to the taffy working as intended, that it tasted great - a sentiment with which Scrooge did not agree. A version of Oxy-Chew also exists in the 2017 Continuum, although it is significantly different from this version.
Oxy-Chew first appeared in DuckTales Remastered. It did not appear in the original NES game on which it was based.