User blog comment:KidVegeta/Canonicity/@comment-3097771-20101130082124

(4)

Lord Slug is non canon, due to its timeline overlooking. This movie could not have taken place, because it is placed after the Vegeta Saga. But, characters such as Piccolo and Tien should be dead at this time. Others, such as Goku and Gohan would have left for Namek already. This could also not be placed after they get back, as Goku would have turned super Saiyan, if need be (which he couldn't, in this movie). Timeline errors are severe canon breaking material, and can not be overlooked.

Final Ruling: Not canon