Dragon ball Z Plothole

[Devauzamaki]

Now Gogeta was only shown in the movies.

So how did Piccolo know about the fusion dance to teach Trunks and Goten.

Goku learn the fusion dance when he was on that alien planet after namek blew up.

So how canon gonna install non canon into its story??

Gotenks shouldn't have been possible for canon. Piccolo shouldn't have known the fusion dance either.

 

[Blizzard3]

Piccolo didn't. Goku showed it to them before he had to go back to other world during buu saga. Besides most movies aren't cannon