If in your tags "Hamlet for some reason" about if your blorbo has a blorbo you are referring to Harker having Hamlet as a blorbo I might be able to answer that!
A few of the key characteristics of Hamlet is his perceived madness, emotional intensity and then desire to bring justice by killing the culprit. Jonathan believes he has gone mad at first and then both he and others think he has succumbed to brain fever, and he then has such desire for vengeance he is willing to sell his soul for it. So it's in a way thematic.
Similarly, Lucy talks about Ophelia and her flowers and it foreshadows her own fate as well as drowning dreams. Jack Seward quotes Polonius ("there is a method in his [Hamlet's] madness"), a character who observes a lot, but understands little (like himself). In that instance he's talking about Renfield, another perceived madman, like Hamlet.
(Aside from Shakespeare being the definitive writer for British people, Stoker worked at the Lyceum theatre)
oh thats so neat actually! guess i have to read hamlet now lol. thanks for the explanation anon!