LORELAI: I bet you’d buy a Barbie for your daughter.
LUKE: Yeah, well, I’d probably give her the cash to buy it herself and meet her by the baseball cards.
Baseball cards are collectible trading cards relating to the sport of baseball. They have been sold since the 19th century.
Little does Luke (or maybe even the writer, John Stephens) know that he actually does have a daughter.
The Annotated Gilmore Girls 