Digimon is actually known as one of the more mature kids' shows out there. With violent imagery, character deaths, and serious family issues like divorce and adoption, you wouldn't necessarily know there are major differences in the Digimon dub. Seriously, where were they drawing the line? But weirdly, Digimon was heavily censored in America. And Digimon isn't the only anime censored in the US. The same thing happened to shows like Dragon Ball Z and Sailor Moon, too.
From touching up the outfits of scantily clad female Digimon to removing everything from guns to incest to Buddhism, 4Kids and Saban turned Toei Animation's original series into a barely recognizable version of itself. While some of these changes detracted from the quality of the series, some actually made it better. The merit of the changes may be up for debate, but one thing's for sure; the sub and the dub are so disparate they may as well be two different series.
At one point in Digimon 01, Sora and Joe find themselves having to fight off a group of ghost Digimon called Bakemon. In the original version, they fend them off with a Buddhist chant. Because apparently religions other than Christianity are poisonous to the minds of American children, this harmless expression of Japanese culture was edited out and replaced with a hokey, bizarre speech about "mind over matter." Afterwards, the children recite a chant they apparently made up on the spot until the ghost Digimon were defeated.
If Digimon is a source of meaningful childhood memories, you might want to skip this bit, because your youth is about to get dropkicked. We're going to talk about incest in anime, and it's not going to be pretty.
While incest wasn't present throughout most of Digimon, it featured heavily in episode 21 of Digimon 01. The director of the episode, Mamoru Hosoda, claimed in an interview that he intentionally wrote the episode as a love triangle between 11-year-old Tai, his 8-year-old sister Kari, and his Digimon partner Koromon. Watching the episode through that lens, it's painfully obvious.
At one point, Kari wets her bed, and Tai covers for her. The way he responds, and the way Kari's voice actress handles the scene, were intentionally written to reflect an abnormal sibling relationship. Also, at one point, Kari says, "no matter how one looks at me, one would know that I am not just worried about my onii-san." Meaning, she's not just worried about Tai as a brother, she's worried about him as a lover. Finally, Hosoda compares Kari to a "30-year-old rightful wife," and Koromon to the "20-year-old naive girl," who are competing for Tai's affections.
The bed-wetting scene, and any other allusions to incest, were swiftly removed from the dub. This, honestly, was probably a good call.
Digimon Tamers is generally regarded as the most lightly censored version of Digimon, not counting later series like Digimon Savers and Digimon Tri that are aimed at an older audience. Unlike Digimon 01 and 02, which completely eliminate the existence of guns, Tamers actually has a Digimon named Gargomon, who carries around multiple guns and ends up shooting them in a wild, out-of-control rampage. So, yes, in both the sub and the dub a dog-man with big floppy ears commits an uncontrolled mass shooting.
What we don't see in the dub are the actual consequences of said shooting. In the American version, you never see any of the bullets hitting anyone. You also never see Renamon scratch Gargomon's face in an attempt to snap him out of his violent fugue state, though you do see the marks on his face later on. So, not only do you have a failure in continuity, you're also showing kids that violent acts and their consequences aren't connected. Not really a great choice, localization team.
In episode 8 of Digimon 01, the kids spend some time relaxing in a public bath. Despite the fact that public baths aren't exactly typical in America, the dub retained the scene. What it didn't retain was the bit where Joe walks into the bath area with a towel between his legs, Tai and Matt decide his reticence to get naked in front of his male friends is unacceptable, and that the proper response is to tackle him and pull his towel off.
While this is meant to be a joke, it's actually a particularly nasty example of boundary violation and physical assault. Since the scene does little besides make Matt and Tai look like bullies, it was probably a good decision to cut this one.