Features another cast member of "Always Sunny in Philadelphia." Rob McElhenney is a fire fighter seen after a building collapse. Glenn Howerton featured earlier in Season 10 as a second year resident.
The title is from the common expression: Where there's smoke, there's fire.
Levine is played by Armin Shimerman, who played Principal Snyder in Buffy the Vampire Slayer. Ken Lerner who played Principal Flutie, Snyder's predecessor, was also in ER, as was Alexandra Lee (young Buffy in episode The Weight of the World).