Creator Backlash: Not the films as a whole, but Steven Spielberg regrets using Those Wacky Nazis as the villains in the original set of films. After making Schindler's List and facing the full reality of the atrocities committed by the Nazis, he came to feel that it was inappropriate to use them as villains in pulpy adventure movies.
Development Hell: A slight case with the fifth Indiana Jones film, which was pushed back two years and went through a handful of creative teams.
Indy's failed attempt to impersonate a Scottish laird in The Last Crusade is an in-character version, if not a Lampshading of this trope, which originated with Harrison Ford attempting to mimic Sean Connery's accent while playing around.
The Nice Hat worn by Dr. Jones has been pretty much consistently popular since the first movie was released and is still being sold in costume shops as well as hat stores. The exact model is a high-crowned Herbert Johnson fedora, if you're interested. Australian hatmakers Akubra (of the eponymous slouch hat) also have a replica model they refer to as The Adventurer.
Similarly, the boots worn by the character for the movies, made by Alden, received their own popularity bump, to the point that they now market their Model 405 work boot as the Indy Boot. (Oddly enough, the character was originally meant to wear Red Wing boots, but either they couldnt get ahold of the right ones, or Harrison Ford wouldnt wear them. Red Wing themselves offer a similar model as the Girard or the 1930s Sport Boot, but only sporadically and usually as an Asian-market exclusive.)
Refitted for Sequel: Lucas is notorious for just not letting go. whatever he has decided should be in the Indy continuity. If money or pacing prevents it from showing up in an installment, it sure will appear in the next.
Temple of Doom included several sequences originally planned for Raiders of the Lost Ark:
Much of the original sword fight that would have been between Indy and the swordsman he shot instead made it into the sword fight at the end of Temple of Doom (where Indy tries the same thing, but his gun is missing).
The minecart chase was originally planned for Raiders (and even storyboarded) but had to be cut for pacing reasons.
Indy visiting Shanghai to retrieve a relic from a powerful local and hiding behind a rolling gong from machine gunfire, as well as the pilots jumping off a plane and Indy escaping in a life raft and down a mountain slope were in the original script for Raiders.
The rolling gong went as far as being storyboarded.
The woman that would become Marion was first envisioned as an old flame of Indy that owned a bar, was a Jazz singer and a double agent for the Nazis. The singer part went to Willie in Doom and the double agent part to Elsa in Crusade.
The first drafts of the third movie had Indy getting in a haunted castle in Scotland. The castle (moved to Austria), the revolving door and even Indy speaking with a poor Scottish accent made it into the final film, but Spielberg didn't want to do another haunted house after Poltergeist. The haunted castle finally showed up in a The Young Indiana Jones Chronicles episode, "Transylvania, January 1918".
The following drafts had Indy retrieving an artifact from an old foe in Mexico, in a scene that payed homage to old Western bar fight scenes. The first episode that (re)introduced teenage Indy in the TV series had a bar fight and Indy retrieving an artifact from a foe made in his childhood (i.e. the previous episode) in Mexico.
Another recurrent idea in these drafts was Indy being attacked by gorillas and then convincing them to turn against his enemies (they were still used in the Mexico prologue, with the enemy using trained gorillas as sidekicks). In Skull, Mutt directs an attack of South American monkeys against the Russians.
An episode of the never produced fourth season of the TV series would have Indy meeting Belloq for the first time and following Percy Fawcett in his (historical) expedition to find a lost city in Brazil. Fawcett later showed up as a secondary character in one of the most important Indy novels, Indiana Jones and the Seven Veils.
Another episode would show the beginning of Indy and Belloq's enmity when he (a friend till then) betrayed Indy and stole a crystal skull they had found in Honduras, leaving Indy to be arrested by the local authorities (and explaining in turn the Noodle Incident mentioned in Doom). In Skull, the crystal skull is the Mcguffin, and Indy is betrayed by an old friend (Mac) and left to be arrested by the US Army in the Nevada desert.
Short-Lived Big Impact: There were only three movies made in the 1980s, but they had a tremendous impact on popular culture then and especially the adventure film genre.
Tribute to Fido: In Real Life as in-story, Indy is named after George Lucas's dog Indiana. In Temple of Doom, Willie was named after Steven Spielberg's dog, and Short Round was named after the dog of another crew member.
You Look Familiar: Every foe Indy fights that is larger than usual, except for Dovchenko in Skull, was played by the late British wrestler and stuntman Pat Roach. That makes the "giant sherpa" and the second German mechanic in Raiders, the Thuggee overseer in Doom and a German World War I pilot in a deleted scene of Crusade. You may know him also as General Kael, The Dragon from another Lucasfilm production, Willow.
Ronald Lacey, who played Toht in Raiders, appears as Heinrich Himmler during the Berlin book-burning in Last Crusade.
Sean Patrick Flanery, teenage Indy in the TV series, cameos as a patient in a mental asylum in Skull.
Paul Freeman, who played Belloq in Raiders, plays one of Indy's allies in the TV series, Great White Hunter Frederick Selous.
Vic Tablian plays one of Indy's Peruvian guides in the prologue of Raiders and the monkey trainer in the Cairo scenes. He returns in the TV series as recurring villain Demetrios, and after Demetrios is killed even shows up as an Armenian (finally Tablian's actual ethnic background) agent working in World War I Istanbul.