Aqui está uma captura de tela da cena mencionada na pergunta:
O veterano ator Richard Jenkins, que interpreta Giles, o melhor amigo gay e vizinho de Elisa Esposito (Sally Hawkins), explica isso. -Rico-Jenkins-plays-gay-shape-water / "> em uma entrevista com Washington Blade :
The seasoned actor is also full of admiration for writer/director Guillermo Del Toro.
“He is amazing, like no one else,” Jenkins says. “He’s really smart. I don’t think there’s a movie he hasn’t seen and he understands what the movies are about. He understands how to speak in film language. Nothing is wasted in his movies. When you see a scene, everything has a purpose, everything has a reason.”
He cites one scene where Sally is waiting for a bus and sees a guy with balloons and a birthday cake with one piece missing. The director said it was the character’s birthday party but he was the only person there. Those few seconds of film, barely noticed by most viewers, expand Del Toro’s visual palette and expand the movie’s theme of lonely people trying to make connections.
O diretor falou sobre ele mesmo em uma entrevista com The Sunday Times , mas está atrás de um paywall:
My favourite intricacy is a man crying at a bus stop, holding a birthday cake.
“That is a vignette,” del Toro says, pleased it was spotted. “This guy threw a party nobody went to, and now he's going home with one slice of cake cut out. He ate it, and he's bringing all the balloons home, too. I was trying to show that Elisa's not lonely. She's very happy. This other guy is lonely.”