To prove to Willow that he's the real Xander, he does the Snoopy Dance, which Willow noted she likes seeing him do when she goes to his house to watch A Charlie Brown Christmas (1965) in S2's Passion (1998).
The "hasty" Xander brushes off Willow's remark, that he did not think earlier about the implication of the situation with Anya, by wondering how she would handle an evil twin. Willow mutters "Well I handled it fine," a reference to her her counterpart from the Wishverse she faced in Doppelgangland (1999).
Riley mentions Buffy's obsession with bad ice skating movies. Buffy's interest in ice skating has been previously mentioned in episodes like What's My Line?: Part 1 (1997).
Riley mentions that Buffy loves bad ice-skating movies. Michelle Trachtenberg, who plays Dawn, went on to star in an ice-skating movie: "Ice Princess" (2005).
When Giles is describing his fight with the Toth, the camera cuts to Willow by the bookcase. One of the books is entitled "The Bedside Playboy." This is a legitimate book of short stories curated by Hugh Hefner in 1963, but not what we would normally expect in a magic shop!