A Shout Out is something subtle (a name, line of dialogue, or prop) in a show that refers to fans or family members of the cast or crew, or to another source of inspiration. By nature, these can be obscure for casual fans.
You can even talk about them in English class if only you call them "allusions". However, remember that many tropes, symbols, and such are older than they look and can, often, [...] [tvtropes.org]