On Deck 13 1/2 is a data dongle. Pick it up to receive a message from the Racist Hot Dog, who instructs you to go into The Cortex and install the dongle at its console. Simply retrace the path taken to reach 5H4DOW-TP during the storyline and look for a jump pad in the large building to launch you up to the insertion point.
Upon inserting the dongle, the Racist Hot Dog calls again and tells you that it's the Birthday Cat's birthday, and he wants you to fight in his special arena as the present. This leads into the next side-mission, I33t H4X0rs.