I have found some really weird coincedences in Pokemon games!
When a Glameow faints, its cry sounds like "mamma mia!"  In a GBA or GBC (cant remember which) Pokemon game, a trainer was named Plumber Mario. In Japan, Ash is known as Satoshi, the first name of the creator of Pokemon. Shigeru Miyamoto is recognized as Tajiri's rival, so Gary is Shigeru in Japan.  Shiny Shroomishes look like Toads from Mario games.  You can meet the programmers of Pokemon games in Saffron City in Pokemon FireRed/LeafGreen, and in Ruby, Sapphire, and Emerald, they are staying in the Cove Lily Hotel.

TELL ME IF YOU KNOW ANY MORE AND I'LL POST 'EM!