Billy Crystal is one of Bill Maher’s guests tonight, and that’s a Real Time booking of the first magnitude. Crystal’s not on the panel – he’s scheduled for the top-of-the-show interview segment – but that still leaves plenty of time for commentary, and hilarity. Panelists this week include Joy Behar and David Frum, who, after tonight, might consider taking their act on the road – billed as Oil and Water.