I spy with my little eye
Throughout the teleplay, Glen repeats the phrase "I spy with my little eye." He does this in a disturbing way, which corrupts the innocent meaning of the phrase, which is commonly used in a children's game. This symbolizes the strange relationship between Glen and Elizabeth.
Forget-me-nots
When Glen first arrives at Elizabeth's house he tells her: "I suppose I ought to have brought you a bunch of flowers... a bunch of forget-me-nots." Forget-me-nots are symbolically significant, representing the fact that Glen thought Elizabeth had forgotten about him.
Glen
Glen himself symbolizes somebody who hasn't grown up. He clearly had a traumatic childhood and hasn't come to terms with the fact his mother didn't choose to bring him up.
Children's stories motifs
During the teleplay, Glen references a number of children's tales and nursery rhymes. For example, he references the song "Hickory Dickory Dock," and the game "I spy with my little eye." Ultimately, this symbolizes the fact that Elizabeth missed out on his childhood.
Elizabeth's maiden name
Glen mentions Elizabeth's maiden name, which represents her identity before she got married and moved on from her past. As such, this name represents her past, including her teenage pregnancy.