Conan O'Brien doesn't have a late-night show anymore ... which will give him ample time to watch Jimmy Kimmel 's -- 'cause he says he's so excited the star is back on the air!

We caught up with the comedian while he was leaving a building in New York City Thursday with "Saturday Night Live" star Ben Marshall -- who we may have thought was his son for just a split second -- and, we asked him if he had a chance to catch Kimmel's show in Brooklyn. Gallery Launch Gallery Getty

Conan said he didn't make it out ... but, it's all good because he can watch it on-air now -- reminding us we can catch Jimmy on the national broadcast again.

Conan tells us truth will always prevail ... though you've gotta fight for it. He then leaves our conversation politely -- right before he's mobb

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