"Your mom went to get the cookies" is an alternate version of "Your dad went to get the milk" or a comeback. It can also mean your mom went to get the cookies for the milk.
A statement implying one to immerse him/herself fully in an activity. To go all out or waste every inch of your soul in an effort to win or succeed. Relates to the term "Go Big or Go Home" in the sense that one should just do it and not dick around while deciding whether they should do it or not.
Jon: I don't really feel like hookin up with HER again, I 'm just not in the mood...