The first neighbor Chloe interviews says he was in "Northrend" running a 17-hour Raid plundering a "Lich King's Barrow", a Very Outdated Raid released in 2009 called Icecrown Citadel. Any players today can finish the Raid in under two hours with little effort.
When Chloe asks if Dan is there, Ella says that "Ella Spinoza" called in sick, instead of "Espinoza".
Ella actually says "El Espinoza", as in "The Espinoza".
Ella actually says "El Espinoza", as in "The Espinoza".
Apartment layout mismatch: Apartment 503 is straight down the hallway from the elevator, while apartment 903 is around a corner a little ways off from the elevator. Generally, apartments and hotels have the same layout on each floor (except for penthouses and suites) and number each unit in matching vertical order: 903 directly above 803, which would be directly above 703, etc.
After Detective Decker secured a warrant to enter Klumpsky's apartment, she, Lucifer, Ella, and Pete began searching for clues as to the identity of Klumpsky's next victim using flashlights. They could have simply turned on the lights.