Something Your dad went out to get
Your dad is never coming back with the Milk.
The act of grabbing your partners extremity of choice and tugging, pulling, and/or handling it in an attempt to, or make a mock gesture of, extracting milk from said extremity. This action is performed while both (or all) participants make glottal grunting noises similar to the Gorons encountered in early 3D Legend of Zelda games such as Majora's Mask & The Ocarina of Time.
Whoever goron-milked my sister is catching overhands like double cheese burgers