Kazoo Voice (Symbol)
In the opening scene of City Lights, a man and a woman speak to a crowd before unveiling a large monument. When they open their mouths to speak, however, their voices have been replaced with the sound of a kazoo. Chaplin uses the sound of a childlike toy to symbolize the fact that these city leaders, these acclaimed orators, are actually talking heads, mechanized agents of the state, who appear to be saying profound things, but whose words are actually nonsense.
Caged Bird (Symbol)
When the Flower Girl goes home at the end of the day, she leans out her apartment window to water some window boxes. When she goes back into the apartment, she brings with her a cage with birds in it. This symbolizes how the girl herself feels caged and cut off from the world, and in particular from romance and the opportunity to be loved by a man, due to her blindness and poverty.
Eating the wrong things (Motif)
The Tramp has a difficult time living a normal everyday life, and makes many huge mistakes throughout the course of the movie. One mistake he makes several times is consuming inedible substances or switching out edible substances for inedible ones. First, he accidentally eats streamers at the dancehall, getting the long strands stuck in his mouth like the spaghetti he's eating. Later, at a party at the Millionaire's mansion, he goes to take some food from a nearby plate, but realizes it's the head of a bald man. At the same party, he accidentally swallows a whistle and every time he breathes, emits a whistling sound. Finally, when he is freshening up at work, he accidentally swaps out some of his coworker's food for a bar of soap, which the coworker ends up consuming, his mouth emitting huge amounts of bubbles. The motif of unwitting and misguided consumption represents the Tramp's incongruousness with the world around him, the fact that he can barely keep it together to consume actual food, a basic necessity of life.
The Flower (Symbol)
Throughout the film we see the Tramp with a flower that he received from the Flower Girl on the street. The flower symbolizes beauty and the Tramp's love for the Flower Girl, as well as the purity that she represents in her innocence and vulnerability. After the Tramp saves the Millionaire from drowning himself, the two of them walk back to the Millionaire's mansion, but before they leave, the Tramp remembers to grab the flower from the nearby bench. While the Tramp isn't very competent or organized, he manages to hold on to the flower, which symbolizes his devotion to his one true love.
Then, at the end of the film, the Flower Girl sees the Tramp without realizing who he is. When she hands him a flower, she feels his hand and recognizes him by touch. The flower here represents her reciprocation of his feelings, and the endurance of the love that they shared, even after she realizes that he is a poor tramp.
The Tramp himself (Symbol)
While the Tramp is the protagonist of the film, he is also something of a symbolic figure himself, a kind of archetypal clown, representing the baser, more childlike, and primitive expressions of the human experience. This is most evident when we see him in the context of other characters in the film, such as when he is preparing to go into the boxing ring. While the men around him look like straightforward people, he is cartoonishly made up, with his goofy mustache, wide eyes, bowler hat, and jacket. In this way, we see him as not quite a real person, but a fantasy of a person, a psychological extension. The Tramp, as much as he is the character through whom we experience the narrative, is also a symbol for a certain kind of cluelessness and innocence, a stand-in for all outcasts, misfits, and eccentrics.
