Answer:
Bears hi-ber-nate dur-ing win-ter.
What makes them similar is that that both Charrington and O'Brien seem to be on Winston's side, i.e. against the Party. Another similarity is that they both end up betraying him, essentially they deceived him by hiding their true intentions from him. Charrington uses a literal disguise, while O'Brien was just pretending to be something he is not.
