
Because you were being SELFISH.
The Big Bang Theory Season 10, Episode 10

you did something
totally SELFISH without worrying
The Big Bang Theory Season 12, Episode 20

How is that SELFISH?
The Big Bang Theory Season 12, Episode 20

Sheldon, you can't be SELFISH.
The Big Bang Theory Season 1, Episode 14

Sheldon, you're being a little SELFISH.
The Big Bang Theory Season 10, Episode 10