When Angel and Cordelia investigated at the gym, Angel asked if there was any use of steroid, since the only remains of the victims are skin. Cordelia also asked if they have seen anyone "green and scaly". This is reference to Go Fish (1998), where the Sunnydale High School swimming team inhaled steroids and become green and scaly creatures.
Willow calls Angel to tell him that Buffy has been resurrected, which results in Angel calling Buffy at the end of Flooded (2001). She and Angel then immediately depart their homes to meet somewhere between Sunnydale and LA, but both are back by their respective following episode. Because the shows were now on different networks, the show-runners were discouraged against having crossovers, so neither actor appears on the other's show.
During this episode it can be seen that each member of Angel Investigations now has a personalized business card (except Angel, presumably due to his lack of surname). It can also be seen that Cordelia's title is Senior Associate, which may be due to the fact she is one of the founding members of the agency.
Nuart Theater is an art house movie theater in Los Angeles.
"Kimota", part of what Marcus says to transfer bodies, is a reference to British superhero Marvelman (the word he needs to say to turn from his secret identity, Micky Moran, to his Marvelman form).