Depends. Is she (coz no way I'm ticking a he) a willing participant or is the person offering the ice cream a sadist? Are we at Baskin Robbins or is the ice cream sucky?
I suppose so long as it's in good fun--and leads to sexual intercourse, of course--I'm in.
Would you hold your thumb out asking for a ride and then tell anyone who stopped that it was just a gag?