A funny internet meme derived from the Mass Effect 2 video game character Miranda Lawson. A Krogan is a type of sentient alien species similar to bipedal Rhinos and particularly love to headbutt, ram, or charge their enemies in the game. The term/phrase, however, is sharply overused by the character whenever this happens.
Miranda Lawson: "Krogan Charging!!! Watch the Krogan! Krogan Charging!!!"