Xander says in 2.20 Go Fish:

“Swim team. Hardly what I call a team. The Yankees, Abbott and Costello. The A. Those were teams.”

He’s referring to the comedy pairing of …

In 3.05 Fredless, Roger Burkle and Angel have the following dialogue:

Roger: “Well, I tell ya, I hadn’t seen a stroke like that since Nicklaus took on Gary Player in the ‘63…”
Angel …

Lorne says in 2.13 Happy Anniversary:

“This garden hue and the horns have kept me out of some key public performances - just once I’d love to ring in a Laker’s …

Spike name-checks the British football club Manchester United in 2.22 Becoming (Part Two).

In the episode 2.04 Inca Mummy Girl, we see Oz (in his first appearance) wearing a New York Islanders (a hockey team) t-shirt.

In 4.02 Living Conditions, Parker mentions the Red Wings, who are Detroit’s NHL hockey team.

In 1.01 City of, Doyle says:

“Well, listen, best of luck to you man. I’ve got some fairly large coin riding on the Vikings tonight, but I’ll be there with you …