Dragon Ball GT's intro sequence is the only Dragon Ball series intro ever to feature nudity (Goku's genitals can be seen as he rises from the water, wrestling a fish.)
Contrary to popular belief, there IS a manga of Dragon Ball GT. However, it came AFTER the anime and was not created by Akira Toriyama, therefore making it unofficial to the official Toriyama-verse.
GT was the brainchild of Toei Animation and was not based on a manga by Akira Toriyama . However, Toriyama did make some contributions to the series, namely sketches of the main characters, their spaceships, and Super Saiyan 4 transformations.
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.