I don't think it's only he manga. It's just that the manga is the ting most consistently written by Toriyama. There are movies that Toriyama didn't write, and ones that he did, like the semi-recen one with Vegeta's brother. Similarly, his story for Dragonball Online contradicts GT, which isn't really in continuity.
I have a message from another time...If we're talking in internet-debate OBD terms, then yes, "canon" material consists solely of the manga, the exception being if the work in question follows the manga so thoroughly it might as well be the manga (ex: One Piece anime).
Personally, I've always felt that so long as it doesn't outright contradict the manga then it's allowed to count as canon. For example, Cooler never shows up in the manga, but that doesn't necessarily negate his existence.
But the Cooler movie can't really go anywhere, can it? Well, unless it's part of the gap of time beween Trunks landing and the Android attack beginning, but I dunno.
As to the One Piece anime, there are some filler arcs, and the majority of the movies aren't canon, with the exception of Strong World.
edited 29th Mar '13 2:17:36 PM by Enlong
I have a message from another time...I like the chance to see Cooler. I'm just offput by "What the fuck did non-Guru Namekians do to mess up their karma so bad? Why the unusual choice in away team? Where did Vegeta come from? How did they get a win?"
edited 29th Mar '13 4:28:56 PM by wanderlustwarrior
No, the Cooler movie doesn't fit anywhere. Goku, Gohan and Piccolo spent the 3 years training in the snow, and Goku could control his Super Saiyan form when he couldn't in the movie. Also Gohan didn't have a tail at this point.
@Enlong
No, that was written by Naho Ooishi.
Why is Bardock in DBO? Is he a Canon Immigrant?
You cannot firmly grasp the true form of Squidward's technique!They have already made jokes about pan, the para para brothers, and probably other things i'm missing. There is/was a DBGTA on You Tube i think it got taken down though; it was mediocre to mildly amusing, so I'm sure TFS could do wonders with the retardedness of the whole baby arc and the trunks cross-dressing thing for that mole rat dude.
Insert snark

Everything in the manga is canon to Dragon Ball. Things only in the anime are canon to the anime adaption of Dragon Ball. Movies are side stories independent of canon, regardless of whether they fit or not. GT is essentially a very very long movie in regard to canon.
You cannot firmly grasp the true form of Squidward's technique!