If you went shopping at the NBA flagship store on Fifth Avenue in Midtown Manhattan on Monday, you may have noticed some very enthusiastic greeters or even very tall, muscular cashiers working at the register. Those greeters and people on the floor of the store wearing name tags were actually NFL players participating in the NFL Players Association externship program. The three-week internship is called an “externship,” representing the real-world experience the pro sports players get to participate in.