It seems as though they forgot about it in the TV show.
The GS Ball has a connection to Celebi. In the Japanese Pokémon Crystal, during months that Nintendo had a promotion, players could receive the GS Ball using the Mobile Phone adapter. The player would deliver the GS Ball to Kurt, and he would analyse it for a day. When you got it back, if you went into the Ilex Forest, you would notice that the trees are shaking (presumably by wind). If you stood in front of the shrine and put the GS Ball in it, Celebi would appear out of nowhere and attack. It was at Lv. 30.
I believe that you can still access the GS Ball event in Crystal using a Game Shark. Look on GameFAQ's and maybe you can find the code for it.
It seems as though the TV show ditches elements for no apparent reason. I mean, why did Ash let Pidgeot go? It doesn't make sense.