Tamara Taylor, who plays community center director Olivia Rawlings in this episode, went on to play Dr. Camille Saroyan in Bones; in that show she is head of the Forensic Division of the Jeffersonian and often works closely with the FBI to solve crimes, as well as a former police officer. Aldis Hodge, who plays suspected shot caller Travis, went on to play Alec Hardison in Leverage; in that show he is a thief/hacker who, along with a team, works outside the law (usually) to solve crimes and right wrongs.
At 18:41 we see a closeup of Charlie's watch. It's a perfect choice for a mathematician with its digital display and a mini calculator built into the wristband. It looks like a precursor to today's smartwatches.
First appearance of both Gary Walker and Robin Brooks.