This joke is sort of complex and you kind of have to know the person who made it. Travis Bickle is a capper/film student who takes his screen name from the Robert Deniro character in "Taxi Driver." Travis, the capper, has a fascination with Jodi Foster, the actress. In real life, a man watched "Taxi Driver" and attempted to assassinate then President Ronald Reagen to show his undying love for Jodi Foster. In the film, Bickle is a Vietnam Vet. So somehow this all makes a warped kind of sense.