Possible Clues:

• He preceded and followed O'Brien
• Jay seen by night owls
• Jay sighted at end of the day
• His tenure was set to end in 2009, to the delight of many, though he's reported to be reconsidering
• O’Brien’s lead-in
• He ''jaws'' at night
• Entertaining Jay
• 'Jaywalker' of late-night TV
• Big name in late-night
• Jay of late-night