O

The letter O. Basically an "Oh" respond but either you're lazy or annoyed.

Nova: Guys! Look! I finally found the actual meaning of life!
Arron: O

Y

Can be interpreted into two meanings.
1: A short of "Why". Seriously, it's a short word. Are you that lazy?
2: Short form of "Yes". This Y form is uncommon and mostly used in countries such as Indonesia.

1: Nelson: I finally have enough money to buy a gun!
Rick: y
2: Terry: Hey, are you okay?
Karen: y