<Li> The prank was used in the web series Red vs. Blue where two of the Red soldiers tell their new recruit to go fetch "elbow grease and headlight fluid" from the store . Their prank backfires when the recruit instead asks for the enemy's flag from the enemy's recruit, mistaking the other base for the store . </Li> <Li> GMC's advertisement for their heavy duty vans and trucks shows a few men failing to move a small boulder . Frustrated and defeated, at once a GMC van backs onto the scene with the surprise of the men upon discovering several large barrels of elbow grease in the rear of the van . </Li>

Where does the saying elbow grease come from