In Platinum and HeartGold & SoulSilver, Bidoof's gender difference has more to it than in any other game. In Diamond & Pearl and every future game after HG/SS, Bidoof's gender difference is that the male has an additional 2 curls on the tail. However in these 3 games, Bidoof's patch of white around the face has a more pronounced bump in between the eyes on the male, with a more flattened bump on the female. Whether this is intentional or not is unknown, but due to the fact it was fixed later in Generation V, it's safe to assume this was a mistake.
The character Looker bares a strong resemblance to Koichi Zenigata, a fictional detective in Monkey Punch's manga series, Lupin the Third. This is most likely intentional since Lupin the Third was released when many of the Game Freak developers were young.
Lilycove City's theme (from Ruby and Sapphire) can be found in Pokemon Platinum. It is played on the Audio System that can be obtained at the Villa in the Resort Area.
The European versions of the game have 'Game Machines' rather than slot machines. As playing slot machines is needed to obtain TM64, the European versions of Platinum will occasionally reward the player with the TM while talking to the Game Corner's receptionist. The reason for this change comes from implementation of more aggressive and strict legislation in the European Union towards gambling.
"Looker", a character who hides his real name, says that he is working to stop Team Galactic from ripping reality into pieces and creating a new world to replace our own. He wears a brown coat and a suit, and has very pointy hair. He seems very similar to "The Doctor" from "Doctor Who". The Doctor goes around stopping galactic cataclysmic events, and never reveals his actual name. "Looker" also looks like the tenth doctor, David Tennant.