During the early parts of the Casa Cristo sequence, Speed and Racer X are duking it out with a set of headhunters. They're doing all sorts of flips and knocks and standard Speed Racer car stunts. Then one of the headhunters goes for one of the other drivers and Racer X flips his car to go after him... and takes him out by punching the driver in the face. In a movie full of the cars doing all the fighting, this was particularly hilarious.
Speed has stalled the Mach 6 during the final race. Pops manages to diagnose the problem and figure out a solution, then Ma Racer asks, "Would Sparky know that?" Cue the Oh Crap looks on the Racer family.
Pops suspects Spritle and Chim-Chim are watching the race, as forbidden. They are, and quickly flip the channel to a nature show. In German.
Pops: "It's in German."
Spritle: "Not the monkey parts."
Which is ironic, because the film was shot in Germany.
Sprittle and Chim-Chim are acting out their favorite anime on the couch when Ma Racer walkes in:
Ma:"What are you two doing?"
Ma:"Is this the same nothing that destroyed my last couch?"