Z often established that people can't keep their bodies if they go to hell. While GT contradicts this (particularly noticeable in the Super 17 arc.), even the original series often disregarded this "rule" and featured villains in hell retaining their bodies in several episodes.
The USA FUNimation VHS and DVD Box Volume 13 shows Pan trapped by Naturon Shenron but he was not in the DVD volume, He was in the previous VHS and DVD volume 12.
The USA FUNimation VHS and DVD Box Volume 12 shows Oceanus Shenron on the VHS and DVD box but she was not in the DVD volume, she was in the previous VHS and DVD volume 11.
In the final episode, Turtle says he's nowhere near a thousand years old, despite having celebrated his thousandth birthday in DBZ, following the Garlic Jr. Saga.
Goku finds Super Android 17 by tracking his Ki. Androids don't have a Ki.
Goku goes Super Saiyan while he has a tail in this series. According to Z, this was impossible.
Krillin has aged into an old man yet Yamcha and Tien, who are OLDER than Krillin, have not.
It was previously established that characters who are killed in the afterlife cease to exist. Yet in this show, when Frieza and Cell are killed in Hell, they simply regenerate endlessly, completely contradicting the original rule.