In Star Wars: The Complete Saga and Indiana Jones: The Original Adventures, Harrison Ford's respective characters from each game appear as a Guest Fighter in the other.
The German pilot who fights Indiana Jones in Raiders of the Lost Ark is played by the same guy who plays the guy who operates the gong in Temple of Doom (the late Pat Roach). In the LEGO version, the German pilot is the guy who operates the gong.
In LEGO Indy 2, the title character is distracted while driving through the warehouse by the sight of you-know-who frozen in carbonite.
The "Shoot First" achievement for killing Greedo can be done with either Han or Indy.
Ike Amadi gives Gorilla Grodd a British accent despite being American.
The British Alfred Pennyworth was voiced by Keith Ferguson and Steve Blum (both of whom were American) for the first two Batman games. This changed in Beyond Gotham when Robin Atkin Downes took over the role.
Fandom Nod: In the "Raiders of the Lost Ark" hub in Lego Indiana Jones 2, we see a pig being roasted. It's not the official LEGO pig, but rather one made by BrickForge.
In most games, the roles aren't done by the original actors, but Clone Wars is an exception, being one of the first games to get the cast from the source (in this case, the show) to voice for the game, they even got James Earl Jones to do some voice clips for Darth Vader.
A good chunk of the voice cast changes for LEGO Batman 3.
Recycled Script: LEGO Marvel seems to take a lot from the first season of The Super Hero Squad Show: a cosmic object has broken and been scattered, so the heroes, based in the Helicarrier, must collect the pieces before Doctor Doom and his army of villains, all ending in Galactus attacking Earth and the two sides forming an Enemy Mine to stop him.
LEGO Star Wars was originally planned to feature Zam Wessel and a level featuring her, and there was even a Dummied Out character model. The Complete Saga gave her a playable slot, and finally included the level that was dropped from the original game.
Darkseid was planned to be playable in LEGO Batman 2, but was dropped, with the only hints left being unusable character data. He was in the final batch of DLC characters in LEGO Batman 3.
Spoiled by the Merchandise: The very first Star Wars game spoiled Revenge of the Sith as it came out about a month before the movie did. The lack of dialogue and changing of a few scenes did create a few deviations. The same thing goes for Pirates, which was released a couple weeks before On Stranger Tides.
Trolling Creator: Due to fan demand for Raven for Beyond Gotham, the official Twitter account started teasing fans about it. Firstly, they jokingly asked if she was even that popular, then pretended to confuse her for Raven-Symoné by tweeting "#RevealRavenSymone". Finally they agreed to reveal Ra...'s Al Ghul.
Some files for the original LEGO Star Wars game shows that Zam Wessel was planned to be in the game, as well as a wheelbike chase with Grievous. They brought Zam back for The Complete Saga, but never used the wheelbike chase, presumably due to already having a driving segment.
Similarly, a level where you played as Anakin against the droid battleship in a Naboo Starfighter was planned for the first game (with a piece of the post-level cinematic shown in trailers) but was scrapped, most likely because Episode 1 already had the podracing level. It was included as a bonus level in The Complete Saga, redesigned to be more like that game's vehicle levels.
Demos for LEGO Marvel Superheroes showed that the Green Goblin could turn into his Ultimate incarnation. They are instead separate characters in the actual game.
Also, Lady Deathstrike was originally going to be in the game, but was cut.
The box art and the mini comic for stage five suggests that Tony was originally meant to upgrade to the Mk. 7. Instead he goes to Mk. 42
In one interview, the designers said they had considered giving Captain America a gun, but they decided it would be too difficult to add with his other abilities.
According to Brickipedia, the Lord of Apokolips himself, Darkseid, has character data that can be found by digging through the game files in LEGO Batman 2: DC Super Heroes. Nora Fries, the cryogenically frozen wife of Mr. Freeze, was also planned, but possibly scrapped due to lack of importance and canonically not making sense as a playable character. Darkseid is a playable character, however, in DLC for LEGO Batman 3.