The phrase "Press F to pay respect" originates from a scene in the video game "Call of Duty: Advanced Warfare" released in 2014. In the scene, players are prompted to press the "F" key on their keyboard to pay their respects at a funeral.
During the original MW2, Soap is higher-ranking than Ghost; being his Captain, while Ghost is his Lieutenant and second-in-command. In MWII, Ghost keeps his rank of Lieutenant, however Soap is lower-rank, being a Sergeant. Ghost affectionately refers to Soap as Johnny,  especially after Alone .