At around the 11 minute mark Angel uncovers Darla's face but when Angel and Drusilla fight in the next scene Darla's face is covered again. Then when Darla wakes up the shot shows her face is uncovered.
Wesley reports that sunset is at 5:47, and sunrise is at 6:15, but in Los Angeles, there is no day of the year in which those times happen, even adjusting for Daylight Saving.
When fighting with Drusilla over Darla, Angel tells her it's the 21st century. The 21st century started January 1, 2001. This episode was the last to air in the 20th century.
(at around 1 min) When the car skids while turning around, a green/yellow mannequin can be seen where Cordelia is supposed to be sitting.
Around 19 minutes in, you can see skid marks from previous takes.
About 15 minutes in, you can see Cordelia mouthing the lines to Angel. (Widescreen only)