In Lie to Me series, the sister of the expert's colleague meets the expert, Cal, for the first time. She says to him: "You are super sexy. Do you want to make out?", and he replies:" Absolutely. Climb on board, darling. Does "climb on board" mean "I agree"? I know that one of the meanings of "on board" is "in agreement with", but why the speaker has used the verb "climb"?