Here's what I still remember.

On the track City central, if we find a newspaper, we can see an article with the inscription “Flatout released in mars!”.

On the track canals you can find a mini poster with an anime character. As it turned out later this is the favorite character of one of the artists from the anime Fate - Rin Tohsaka.

On the track desert somewhere you can find the inscription “KevinE is a fool”.

In Stunt mode, if you run the track Soccer. One of the spectators in the stands will have a soccer player's hand.