what the sigma

That video of Squidward hearing that Spongebob got the promotion before him

Refers to something absolutely mind boggling that your homie has to say

"Ermmm... What the sigma"

Person 1: Did you hear what Miss Hennessey did to her class on friday?
Person 2: Uhhhh no?
P 1: Well just in short... (tells something absolutely crazy and unbelievable)
P 2: Erm... What the sigma