Aggression is the title of a sketch featured in The Muppet Show: Sex and Violence. The sketch begins with two heaps, who are described in the script as follows:
After the heaps beat each other up for a bit, two stalks enter. The pink stalk prompts the gold stalk to get acquainted with the heaps. However, when the stalk pokes one of the heaps to get their attention, they both attack him. The pink stalk tries to pacify her injured friend, who survived the blow with a twisted nose.
The characters featured are listed in the script as "Green Heap," "Purple Heap," "Pink Stalk," and "Gold Stalk" (although the stalks refer to each other in the script as "George" and "Martha").
The title of the sketch, along with script notes, were released by Karen Falk (Henson Company archivist) in an installment of Ask Henson.com.