Unusual Birth/Early Childhood Bilbo had quite the unsuaul childhood, being born a hobbit. He lived in a hobbit hole with one part of his family being quite respectable people, and the other quite adventurous people.
The call to adventure Gandalf puts a mark on Bilbo's door that states he is a burglar.
Crossing the Threshold Bilbo leaves with Gandalf and the dwarves to finally start their journey, leaving the safety and warmth of his hobbit hole.
The challenges or trials Bilbo faces many challenges in the books, such as the goblins, trolls, wargs, and Smaug. This is how he gains his experience.
Supernatural Mentor Gandalf is Bilbo's supernatural helper or mentor, he mentors him and eventually leaves for Bilbo to learn on his own.
The Special Weapon Bilbo's special weapon is the magical ring obtained from Gollum. He can turn invisible using this ring, and it is a one-in-a-kind weapon.