Here, also, there’s a rather glaring plot hole that will become clear in episode 4: Kero-chan tells Sakura to try using the new Fly card, before Sakura writes her name on it. But I suppose there’s some No-Prize answer out there; after all, it’s MAGIC.
This is really belated on my part, but I think I filled in the plot hole. I was re-watching episode one of Cardcaptor Sakura today, and had a thought:
Maybe Sakura can use Fly without writing her name on the card because she didn’t call Fly out of the card. That is, Fly didn’t appear before her. Instead, Fly enhanced the wand. The wand/key probably has enough control over the cards (being the item able to convert them back into cards, with thanks to Sakura’s magical abilities) that it can take on a card’s powers (growing wings from Fly) without the need for Sakura writing her name on the card.
This of course ignores the part where Sakura uses The Windy without writing her name on it. Maybe The Windy felt responsible for letting all the other cards go? Or maybe Sakura has a natural affinity to The Windy that is conveniently never mentioned?