Bear is a supporting stuffed animal in Rick Yancey's The 5th Wave.
Bear was a consoling device for Sammy before and during the Arrival. When the soldiers of Wright-Patterson AFB arrive at Camp Ashpit to take the children to safety, Sammy decides he needs to be a "big boy" and give Bear to Cassie to comfort her until he gets back.
When Cassie and Sam are reunited, she returns Bear to him but he begins to reject it. He claims that he is a soldier now and 'soldiers don't have bears'. Cassie has taken to keeping Bear with her now.
Over time, Bear found its way into Megan's hands. She decided to name it Captain. That caused some fighting between her and Sam as he argued that Bear's name is Bear while she argued that it wasn't a name. When Cassie and Ringer were going off to Camp Haven II Sam tried to give Bear to her so that she could return to him just like she did before but she refused it.
When Ringer's daughter Cassie was born, Sam gave it to her. It has started to become a bit faded but baby Cassie loves it all the same.
Facts and Trivia
While Sammy is at Wright-Patterson, Bear is portrayed by Cassie as being a motivator to keep a promise to Sammy, concerning the survival of Sammy. Bear itself is also a promise that contributes to influence Cassie to find Sammy (that Cassie would be able to keep Bear safe and not lose him).