This chapter takes place "years before" Fantastic Four (Marvel, 1961 series) #1. The events of this issue occur in the mid to late 1980s. Although this story implies that the Fantastic Four debuted in the early 1990s, the introduction of the Fantastic Four will be pushed further and further into the future due to Marvel Comics' sliding timeline, however the events of this series will remain fixed in time.
First appearance of all members of the First Line featured herein, except for the Eternal Brain and Yeti. The Eternal Brain previously appeared in Red Raven Comics (Marvel, 1940 series) #1 (August 1940) and Avengers Forever (Marvel, 1998 series) #11 (November 1999). Yeti previously appeared in Fantastic Four (Marvel, 1961 series) #99 (June 1970). First appearance of Mako, Nocturne, and Korya.
According to Official Handbook of the Marvel Universe: Teams 2005 (Marvel, 2005 series) #1, Makkari was present during the battle. He may be the speedster seen on page 16 panel 1.
Cassandra Locke, Pixie, Makkari, and Yeti are the only known survivors of the explosion at the end of this issue. Cassandra's next chronological appearance is in issue #10. Pixie's next chronological appearance is in issue #1, followed by X-Men: The Hidden Years (Marvel, 1999 series) #16. Makkari's next chronological appearance is in The Eternals (Marvel, 1976 series) #5. Yeti's next chronological appearance is in X-Men: The Hidden Years (Marvel, 1999 series) #16, followed closely by issue #7 of this series (retelling the events of Fantastic Four (Marvel, 1961 series) #99).
The Knight Templar is only called by his full superhero name in the letters page of issue #8. All mentions of his name within the stories themselves refer to him simply as "Templar".
It is unclear if Mako is a member of the First Line in this issue or merely under the supervision of the Knight Templar.
The character on page 3 with the triangular goggles appears to be Katyusha, who is formally introduced in issue #7.
The female Skrull, Korya, began seducing Yeti beginning in issue #11. Due to her manipulations, Yeti became a Skrull sympathizer. Korya's name was revealed in Marvel Encyclopedia Volume 6: Fantastic Four (Marvel, 2004).
Doctor Strange's appearance here is explained in the letters pages of this issue and issue #5: He spent years in Asia, learning his craft at the side of the Ancient One, before returning to America to become a practicing mystic master. In fact, in his very first appearance (Strange Tales #110), it was revealed that the name of Doctor Strange was already "spoken in whispers". According to Roger Stern, it's quite possible that the Doctor Strange stories up through Strange Tales #122 actually took place before Fantastic Four #1.
Thunderbolt Ross is shown on the Watcher's monitor wearing two stars on each of his shoulders, making him a Major General in the U.S. Air Force at the time of this story.