A classic by dra2k4
The 'balls' joke is a must have for Pokémon Trainer comics. It's too good to miss.
No need for a visual aid by dra2k5
Just close your eyes and think. ;)

Previous Knowledge expected to understand this strip:
The bag or satchel the main character gets in Pokémon can carry many items and carry 99 of each thing and many other things including a bike.
Trainers throw a pokéball to release a Pokémon.
Pokéballs just happens to be the ideal alternative way to refer to some things so not to pollute minors.