Brainy Baby: One is only a one-year-old, yet she understands the concept of "one more" and "one less".
Contrived Coincidence: The four that Four lands on just happens to be on the toy train.
Dissonant Serenity: The man in the suit is completely unfazed by an anthropomorphic number jumping out at him, and his response to having a doppelganger isn't to wonder what the heck's going on, but simply to get peeved.
Expendable Clone: The man's doppelganger is sent away without fanfare.
Me's a Crowd: Five imagines a bird being cloned indefinitely.
No Antagonist: This episode's conflict isn't caused by a Meanie, but rather by One, who is just a clueless baby.