Pheagle stopped and stared at his custom Pokéball. He hadn't caught any Pokémon with it yet, so why the hell as it moving?!? Suddenly, it popped open, revealing that it was full of a strange green goo!
The goo quickly escaped the ball and started flowing towards Pheagle, engulfing his shoes!
Next, it rode up his legs, causing them to turn purple and increase in size, shredding his shorts! His feet also grew and turned into strange purple blobs, bursting through his shoes!
His legs continued to expand, while a strange bump exploded from the seat of his shorts, revealing a large, plump tail with three green spots and a curled tip. His shorts were all but destroyed by now.
The goo continued to climb up Pheagle's body, this time crawling under his shirt, causing his belly to expand, snapping his belt and ripping apart his green shirt!
Panicked, Pheagle yelled for the strange goo to get off him, but it just ignored his pleas and continued changing the rest of his body. His arms were next, and they burst through his shirt sleeves as they expanded!
His hands soon followed, shredding his gloves as they morphed into purple blobs! He looked at them in shock as his belly continued to expand, ripping his shirt even more!
Finally, the good reached Pheagle's head. It completely engulfed his entire cranium, knocking his hat off, and then covered his face, muffling his cries for help! As Pheagle's face morphed into that of a Goodra, he stared, confused.
Large antennae stretched from atop Pheagle's new head, and he began to emit goo from his body...in fact it was just about the only thing he could say now!
"Goodra!?" Pheagle said as he surveyed his new body. He was now a chubby dragon Pokémon! Hopefully no one would find out and try to catch him!
it's basically a special ball designed to catch/hold celebi. but it serves no purpose in the anime, but it's used to summon a celebi in crystal, and gets handed over to kurt in johto
https://bulbapedia.bulbagarden.net/wiki/GS_Ball it's basically a special ball designed to catch/hol