Just wait for Hank Azaria.

Whatever you do, do not be put off by the rather awful opening 40 minutes of “Night at the Museum: Battle of the Smithsonian.”

Once Azaria shows up as a nasty Egyptian pharaoh with a hilarious Boris Karloff lisp, it’s a whole different movie. And there’s so much rollicking invention and inspired surreal craziness that truly takes wing in the movie that you won’t mind at all the many moments when the script persists in crashing the movie to earth with a sickening thud.

Actually, there’s a reason for all those thuds, if you think about it.

This sequel to the irresistible 2006 smash hit comes under the category “family film,” which, of course, really means: “Kid’s film with parents and older siblings welcome, too.” And it makes sense that a certain amount of dreary Hollywood industrial cliche-mongering would be absolutely necessary to keep the little ones nestled inside the movie’s plot instead of careening around in their seats on the cerebral equivalent of a sugar high.

"Night at the Museum: Battle of the Smithsonian"

Three stars

Ben Stiller, Robin Williams, Amy Adams, left, Hank Azaria and Owen Wilson in Shawn Levy’s follow-up to the hit comic fantasy about museum exhibits coming to crazy life when the sun goes down.

105 minutes.

Rated PG.

Now playing in area theaters.

The movie has to plod for those initial 40 minutes— and for periodic spots afterward—so that when it zooms into the comic stratosphere, it does so with such cheeky hilarity that it’s everything kids (and their parents) deserve.

The original, you may remember, was about a night security guard in New York City’s Museum of Natural History who redeems his reputation with his young son by being there when every exhibit in the joint suddenly starts coming to life — woolly mammoths, skeletons of dinosaurs, and Easter Island statues (they chew gum) as well as Teddy Roosevelt and the object of TR’s secret museum yearning, Sacajawea. It was based on a children’s book by Milan Trenc, and the basic idea— museum exhibits wildly come to life—was a giddy and nutty natural in the age of digital animation.

The idea here in the sequel is that our security guard (Ben Stiller) has suddenly become a big success on TV infomercials. He’s a phony but tireless and wealthy pitchman like Ron Popeil, then. He interviews George Foreman on the air and tries to sell people glow-in-the-dark flashlights.

In the meantime, his nasty old nemesis at the Museum of Natural History — played by Ricky Gervais with the usual snaggletoothed zest—has decided to pack off all the museum’s exhibits and send them to “deep storage in the federal archives,”

i. e., a huge cavern under the Smithsonian Institution where all old museum exhibits presumably go after they’ve been pronounced dead and boring by dim-bulb cultural bureaucrats everywhere.

So, on an errand of nostalgic mercy, the former museum guard goes off to the Smithsonian to liberate his old friends from the archival burial that is our society’s way of thumbing its nose at history.

And that’s when the movie slowly rouses itself from industrial death. That’s when Azaria shows up as Kahmunrah, with his villain’s ego and wicked lisp. That’s when Amy Adams arrives in delicious updated Katharine Hepburn mode as Amelia Earhart. That’s when “the biggest museum in the world” starts “coming to life” and taking sides.

On the nasty lisping Pharaoh’s side, you’ve got Al Capone, Ivan the Terrible (a droll Christopher Guest) and, until Kahmunrah puts them in their place, Darth Vader and Oscar the Grouch. (Their dressing down by the Pharaoh is one of the movie’s delightful moments.)

On the good guy side are, of course, the stone Abraham Lincoln of the Lincoln Memorial and miscellaneous museum types like General Custer (who charges heedlessly into battle yelling “We’re Americans! We don’t plan, WE DO!”) and a rather height-sensitive Napoleon Bonaparte.

Much nonsense about Pi and ancient Egyptian tomb locks is thrown away as “plot” so that the movie can get down to the real business of piling up glorious visual improvisations of the sort the great Warner Bros. cartoon geniuses would have loved.

My favorites, frankly, are the immortal paintings and photographs that suddenly come to life and aid the cause — the pitchfork held by Grant Wood’s “American Gothic” farmer becomes a weapon, Edward Hopper’s “Nighthawks” are moved to leave the diner and one of J. M. W. Turner’s swirling seascapes is upended and poured over a giant octopus who needs wetting down. Amelia suddenly starts pirouetting with one of Degas’ ballerinas. By the time, you get to putti — which is what the Italians call all those Cupids in paintings — dancing around to the Bee Gees’ “More Than a Woman,” the movie swings.

Pop culture collides with conventional culture and, for those who haven’t bothered to notice, the kids in the audience are getting a heck of an educational blast of museum culture while they’re being royally entertained.

Don’t begrudge this comic fantasy its solid pedestal of megaton concrete.

Those aren’t feet, they’re just boots. Once the movie slips out of those, it really flies.