Ever since Iron Man introduced Nick Fury in a post-credits stinger every blockbuster movie has felt the need to do the same. Sometimes it's done really well, adding a great final beat or an exciting tease to the film. Sometimes it's The Amazing Spider-Man (we're trying to parse out that mid-credits sting right here. Expect spoilers).
The history of post-credits stinger is fairly recent... since post-movie credits are fairly recent. It wasn't until the 70s that it became firmly established that there would be a long credit roll at the end of a film, and in the decades since that roll has only gotten longer as more people get noticed - caterers! Payroll! - and as FX teams swell in size (as always there are some exceptions. Around the World in 80 Days had a seven minute animated closing credits in 1956, one of the first films to have closing credits).
So sitting through credits can be a task, and it's nice to be rewarded for it. But the reward should be good - The Phantom Menace faded to black and had the sound of Darth Vader's breathing, a nice bit of 'foreshadowing' but not much of a stinger.
I've compiled a list of what I believe to be the five best post-credits stingers, and I'm presenting them in chronological order. Argue with me in the comments.
The Muppet Movie
In 1978 Animal House may have had the first real post-credits gag (an altered 'Visit Universal Studios' card that was standard on Universal releases at the time), but The Muppet Movie got it right for the first time. The film's credits begin to roll as Sweetums bursts through the movie screen, finally catching up with the Muppets. It turns out we're in the Muppet screening room, and during the credits there are a ton of gags (the 70s and early 80s were the heyday of 'during the credits' jokes and bloopers. Dom Deluise is the patron saint of these). Then, as the credits finally end the camera focuses on Animal, who yells "Go home! Go home! Bye-bye!" Ferris Bueller's Day Off would steal this a couple of years later.
One last gag! After all the credits roll the film returns to the original airport, and we see the taxi that Ted Stryker had been driving at the beginning of the movie, still up on the curb. The meter is running. The guy in the backseat looks at his watch and says "Well, I'll give him another 20 minutes... but that's it."
Like Airplane!, Idiocracy's stinger is an opportunity for one last gag, this time featuring Upgrayedd. We see him wake from crogenic sleep, get himself together and walk down a street of the future, checking out girls and saying "Imma find this ho." It's like a joke on the very concept of post-credits teasers for sequels - and it's a great cap to the running gag of Upgrayedd.
By the time the fifth film in the Fast and the Furious franchise hit, mid-credits stingers (coming after all the above the line people, just before the below the line) were de rigeur. They tended to be either toss-off jokes or clunky reveals that the villain wasn't dead or that another villain was waiting. Fast Five's reveal is so good, though, that I gasped out loud in the theater. Hobbs is at his desk, doing paperwork, when Eva Mendes' 2 Fast 2 Furious character Monica walks in. That alone would have been an okay post-credits stinger, but the good stuff was yet to come - she shows Hobbs a file about a new gang hijacking trucks. Hobbs isn't interested if it isn't Toretto's team, but Monica insists he is. Hobbs leafs through the pages and reveals that the head of the new gang is... Michelle Rodriguez' Letty, who died in the last film! It's a great 'Aw shit!' moment in a movie that expertly tied up the sprawling franchise's loose ends, bringing everybody finally together.
The Thanos reveal is interesting, but the final sting- available only in the US - is one of the all-time best. The shot of the Avengers sitting around, post-battle, silently enjoying some shwarma, has hit the collective pop consciousness like hammer. The scene is technically a throwaway joke, but it sums up everything we liked about the movie - the sheer joy of seeing these iconic characters hanging out together. It helps that Mark Ruffalo is visibly having a hard time keeping a straight face.