Late Night

Dave Grohl is super proud of his mom's new book about raising him ... but when it comes to describing the kind of kid Dave was growing up ... well, he stepped in and ended that conversation!

We got Dave and his mother, Virginia, in NYC Wednesday -- where she kicked off her tour for her new book, "From Cradle to Stage: Stories From the Mothers Who Rocked and Raised Rock Stars," on 'The Late Show.'

David Letterman's never looked so happy to NOT be hosting the 'Late Show,' and told us ... more power to Stephen Colbert for killing it in the ratings.

We got Dave and his massive beard out in NYC Monday -- he joked it's the first time he's been outside in a month, but by the looks of him it could be true. He let us in on his new daily grooming routine, and talked about his old late night stomping grounds.

You'd think he's missing it these days with all the Trump-related material that seems prime for a Top 10 list. Instead, he paid Colbert a nice compliment and made it clear he's thrilled to be doing nothing.

Justin Trudeau wants a rematch with Matthew Perry after getting his ass kicked in grade school and Matt telling the world about it -- FIGHT!!!

The Canadian PM said "I've been giving it some thought, and you know what, who hasn't wanted to punch Chandler? How about a rematch @MatthewPerry?"

You'll recall ... Matt went on Kimmel earlier this month and told the story of how he once beat up a younger Trudeau for "excelling in a sport."

Now, JT tweeted the challenge on April Fool's day, so chances are he's joking. But it would be awesome!

As long as nothing happened to Trudeau's face, that is.

CBS honcho Les Moonves undeniably has the Midas touch when it comes to picking shows and talent, but he swears he did NOT have a premonition Donald Trump would become prez when he tapped Stephen Colbert to replace David Letterman.

Colbert has been king of the heap in the ratings, topping Jimmy Fallon in late night. Conventional wisdom is that Donald Trump has given Colbert the firepower to become #1.

Matthew Perry once beat up Canada's Prime Minister, Justin Trudeau ... and he thinks it pushed the guy into politics.

Matt was on "Jimmy Kimmel Live!" Wednesday, and he told the story of how he and his buddy beat up a 3rd grade Justin for "excelling in a sport."

It's pretty funny -- Justin's dad was the PM at the time and didn't have security around his boy. Jimmy rightly points out nobody could get away with that around Barron Trump.

Even crazier ... Matt doesn't think Justin would be where he is today without that pounding.

Yes, Chandler beat up this stud ... could that BE any more wrong?

Bell Biv DeVoe and Lady Antebellum have a serious connection, and they're taking it to the studio ... according to BBD's Ricky Bell.

We got Bell at LAX -- fresh off BBD's killer mashup with LA on "Jimmy Kimmel Live!" -- and he was still buzzing about the performance. So much so, he says both groups are planning to keep the party going.

He says they already have the perfect name for their supergroup, but there's just one detail left to hammer out.

Mike Posner's father passed away last week, and his son honored him by performing at his funeral ... after revealing the man had cancer last year on TV.

Mike's dad, Jon, died last Wednesday from his months-long battle with cancer at the age of 73 -- and Mike chose to remember him in song by covering a classic.

The singer performed Bright Eyes' "First Day Of My Life" in front of an audience Friday at the Ira Kaufman Chapel in Southfield, Michigan, where Jon was an attorney.

Back in May, Mike had alluded to his father's illness while performing on "Conan," where he changed the lyrics to his hit song "I Took a Pill in Ibiza" to ...

And my dad has cancer
I'm still wrapping my head 'round that
Sat by the hospital bed, nurses poked in their heads
And asked me to sign autographs
And my dad has cancer!
I shouldn't be here, I should be home
But in case you couldn't tell, I'm busy playing myself
In this little Mike Posner show

Nothing's cooler than that.

Carrie Fisher and Garry Shandling shared a stage together on late-night once upon a time ... and we got a clip of the rerun that's re-airing this week.

Antenna TV will be running an old episode of "The Tonight Show Starring Johnny Carson" Wednesday night, with Carrie and Garry as his guests in '83. It's as classic a Hollywood moment as they come.

As we reported ... the 2 stars both passed away unexpectedly this year -- Carrie from cardiac arrest and Garry from a blood clot. Here's to better times.

If someone told Meghan Trainor to "break a leg" before her 'Tonight Show' appearance -- she took it way too seriously.

She performed her song, "Me Too" Thursday night and turned to face her band for the BIG finish ... which was great. Not so great her pivot back to the microphone.

And you know what always makes a fall worse -- fighting it. Watch ... you'll cringe and then laugh, which is okay since her camp says she didn't get injured.

Chris Christie finally explained his awkward face behind Donald Trump after Super Tuesday, and the Guv insists he was NOT being held against his will ... as the Internet believes.

Christie traded blows with Jimmy Fallon on "The Tonight" show ... comparing his infamous stance with Trump to what Jimmy would look like standing behind Jay Leno. -- but of course Fallon got the last laugh.

Watch the clip, Christie claims there really was a reason he looked that way. Not sure Fallon bought it though.

Zayn Malik and Gigi Hadid got all handsy with each other Saturday night, proving their relationship with clear and convincing evidence.

Zayn and Gigi left their favorite night spot -- The Nice Guy in WeHo at around 2:30 AM -- holding hands.

It's sort of a right of passage ... first going through back doors, then walking in separately, but eventually interlocking fingers.

Gavin Rossdale hit the club scene Saturday night, and spent a little time with "Sharknado" survivor Tara Reid.

David Letterman just got the highest beard praise possible ... because it came from ZZ Top guitarist Billy Gibbons.

We caught Gibbons at LAX and asked him to rate Letterman's scruff on a scale from 1 to 10. The bearded legend, who's been rocking his own face piece since the late '70s ... gave us an honest assessment of Dave's.

Check it out ... Billy doesn't think Letterman quite has what it takes to pull off Ol' St. Nick just yet -- but he might wanna pick up a few guitar chords. Ya never know ...

Conan O'Brien's no Fat Jewish -- he insists he and his staff came up with the jokes they're accused of stealing from a blogger ... who's not all that original anyway, according to Conan's new legal docs.

Robert Kaseberg sued Conan for copyright infringement, claiming several of his monologue jokes were lifted from Kaseberg's online blog -- but Conan responded to the suit this week, saying his material is 100% "independently created."

Truth is, some of the jokes are very similar -- but Conan says Kaseberg's comedy was so general and based on current events, it can't be copyrighted. For instance, they wrote almost identical shrinkage quips about an announcement the Washington Monument is 10 inches shorter than previously thought.

Conan's kinda calling Kaseberg's jokes lame. Yes, that also comes off like a shot at his own monologue writers, but Conan's bigger point is you can't steal something so unoriginal.

For the first time, Harrison Ford tried to reveal the details of his plane crash, but the problem is ... HE DOESN'T REMEMBER MOST OF IT!!

It's pretty incredible -- Harrison was trying to tell Jimmy Kimmel about that day back in March when he made the emergency landing of a single engine WW2 plane on a golf course -- but the last thing he can recall is telling the tower ... this isn't going to end well.

Harrison explained why he's suffering amnesia -- check it out.

Jimmy Fallon's going to run out of fingers to injure at this pace ... but he doesn't seem the least bit rattled after cutting his right hand on a shattered bottle of booze.

Jimmy posted a shot of the his bandaged right index finger, saying ... "Nothing that a few band aids couldn't fix."

TMZ broke the story ... Jimmy was partying with the Harvard Lampoon crew Saturday night, and carrying a bottle of Jägermeister, when he tripped over someone. It sounded bad, but Jimmy seems unfazed ... especially when compared to his more horrific left hand injury.