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.
Pops Racer battles a Ninja. As he goes for a backbreaker, the camera zooms in on his GRECO-ROMAN WRESTLING STATE CHAMPIONSHIP RING. Cue pwnage.
Trixie: Was that a ninja?! Pops: More like a nonja. Terrible what passes for a ninja these days.
To fully appreciate this scene, you really have to see the Ninja's reaction to noticing the ring (at the same moment that he is put in the hold, and also the same moment that the audience gets to see the ring). His reaction is palpable.
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 Speed 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.
Spritle and Chim-Chim are acting out their favorite anime on the couch when Ma Racer walks in:
Ma: What are you two doing?
Ma: Is this the same nothing that destroyed my last couch?
During the Casa Cristo, at the point where Speed and Trixie are arguing, Racer X cuts in with a "Children, focus!" that sounds exactly like an older brother telling off his little brother. It's funny every single time.
After the heart-to-heart between father and son, and Togokhan bringing the race invitation, Pops finding out that Sparky had been in the kitchen listening in.
Pops: What were you doing in there!? Sparky: Same thing as everybody else. [Cue Mom, Trixie, Spritle and Chim-Chim sheepishly coming out of hiding too.]
Just before Speed and Trixie kiss in victory lane, the movie pauses as Spritle and Chim-Chim, dressed as doctors, pop up to warn the audience of the disgustingness of the action about to take place.