As Mater accidentally drifts through a building early in the race, the Cars versions of Mike and Sully (from the clip of "Monster Trucks, Inc." in the credits of Cars (2006)) can be seen during Mater's exit.
When Mater drifts through the sushi shop in Tokyo, the sign outside reads (in Japanese), "Hari-Hausens." "Harryhausens" is the name of the sushi shop in Monster's Inc. where Mike and Sully first encounter Boo, the little girl.
The Tokyo that Mater is in reappeared in Cars 2 (2011) as the Tokyo for the first World Grand Prix Race.
At the end, D.J. (a member of the Delinquent Road Hazards and Tuner cars) can be seen in the crowd dancing (and possibly playing the music) with everybody else celebrating Mater's victory against Kabuto. He was also in the beginning, drifting with Wingo and Boost.