Joey Durban (James Carpinello) is Root's (Amy Acker) husband in real life and was the POI from Mission Creep (2011).
This is the first time that Harold has chosen a bird of prey (Osprey) as his alias. The other bird names have been songbirds (Wren and Finch) or fish-eating birds (Gull and Whistler).
Synecdoche is a rhetorical term where a part of something is used to label the whole. Among the most commonly used of these expressions is "The White House", which refers to the Executive Branch of the United States Government (i.e. the office of the President of the United States.) In other uses, an individual proffering assistance might offer to "lend a hand", the hand serving as a metaphor for the whole person.
Freon wasn't the first controversial discovery by Thomas Midgley Jr. Previously he discovered that the toxic compound tetraethyl lead, when used as an "anti-knock" gasoline additive, made the automobile internal combustion engine incredibly more efficient. His discovery resulted in world-wide lead contamination in the environment.
The computer virus Harold works with ("Ice 9") shares the name as a deadly form of water that freezes at room temperature from the Kurt Vonnegut Jr. novel "Cat's Cradle".