Simple game! The first poster gives out the name of a Pokémon, then the second poster gives out the name of another Pokémon that starts with the last letter of the previous Pokémon's name, and so on and so forth. Example:
I'll start with...
Lucario
Poster #1 said:Sneasler
Poster #2 said:Rapidash
Poster #3 said:Haxorus
I'll start with...
Lucario