Both are fun and worthwhile, but it's the former that will be fuelling the most post-screening discussion and speculation – here's what you need to know about what goes on.
The Scorpion Wants Revenge
Michael Keaton's Adrian Toomes, AKA Vulture, thwarted by Spider-Man, is incarcerated for trying to steal a plane-load of Tony Stark's technology (and fuelling a black market of weaponry based on stolen chitari technology.) Walking through a hallway in-line with other inmates, he runs into Michael Mando's Mac Gargan, who was seen earlier in the film as part of the weapons deal Spidey broke up on the Staten Island Ferry. Gargan interrogates Toomes for Spider-Man's identity, which Toomes protects, having come to respect the young wall crawler for saving him at the end of their confrontation, in addition to Peter's proximity to his daughter and Toomes' disinterest in selling out a teenager to a bunch of sociopathic criminals. Gargan responds by saying that when he gets out, he and some guys he knows are going to go after the web-slinger to smoosh him for good.
Mac Gargan's relevance to Spider-Man isn't stated directly, but the prominent scorpion tattoo on his neck makes it clear to anyone with knowledge of Spider-Man's rogue's gallery who he's meant to be – Scorpion (not to mention Mando spilling the beans on social media days before the film opened.)
Scopion is a Stan Lee/Steve Ditko creation who debuted back in 1965 as a villain who held many of the same powers as Spider-Man. J Jonah Jameson, desperate to get a proper track on the web-slinger, funds private investigator Mac Gargan to take part in a set of experiments to give him the powers of a scorpion. The experiment was successful, giving Mac Gargan heightened strength, speed, stamina, and durability, as well as a 'scorpion-sense' akin to Spidey's spider-sense. To complete his super-villain look, Mac Gargan was given a green scorpion suit that included a heavy hammer-tail.
As one of Spider-Man's most dangerous recurring antagonists, Scorpion has beaten him several times throughout their history. Between his obsession with defeating the friendly neighborhood hero and his frail sanity - thanks to his animal-like mutations - the green-suited wrongdoer is one of the most interesting of Parker's foes, often presenting a mirror-image of what Spider-Man could be if he let his morals slip too much.
Homecoming keeps its version of Scorpion close to its chest, not hinting at his origins or what powers he may possess. What this scene does establish is that Marvel is trying to keep the use of villains from other Spider-Man movies to a minimum, with Scorpion being the second major villain that was previously unused in live-action. Second is that Mac Gargan has friends, and that The Shocker and Vulture working together is only the start of the kind of trouble to come for the MCU's Spider-Man. Sony has wanted to do a Sinister Six film for years now, and their mandate of including more villains that necessary has previously tanked two Spider-Man film series. Homecoming is a much more balanced picture in the multi-antagonist department, and Marvel is likely all too aware of where previous attempts went wrong, but it does sound like they aren't against seeing Spider-Man eventually square off against The Sinister Six in the MCU.
Captain America's PSA
Who said Marvel isn't a good sport? In the vein of Howard the Duck in Guardians of the Galaxy's post-credits scene, Marvel decided to use this second tease to have Chris Evans' Captain America come on-screen and rattle off a cheeky bit about how patience is a virtue and how sometimes things you wait for can be disappointing. It's delivered in the same style as the Cap motivational videos being used in Peter's high school, as seen in the trailers.
The clip continues to echo the John Hughes style director Jon Watts was targeting, even bearing a resemblance to the post-credits scene in Ferris Bueller's day off. Since Deadpool already properly aped that scene, though, Homecoming's final stinger only bears a loose resemblence while maintinging the "why are you still here?" joke with the audience.
Although some may be disappointed that this isn't a tease for another big MCU crossover, Marvel's refusal to step out of Peter's world even in post-credits is in-keeping with Feige's comments on the Homcoming sequel. Parker is going to represent a “grounded, realistic” corner of the MCU, and post-Avengers: Infinity War after he helps beat Thanos, Peter will be returning to high school and his normal life. Given the road it's been to get Spider-Man here, and what's coming for he and all the other big heroes of the Marvel Cinematic Universe, this scene is a funny, light-hearted way for Marvel to remind us they're fully aware of all our expectations and that we'll have to wait and see what's next.
It's also a subtle way of telling us we won't be seeing anything of Avengers: Infinity War until they decide they're ready to show us – patience may be a virtue, but it's rarely a fun one.