Robin Williams in Night at the Museum 3 is heart-wrenching to watch (VIDEO)

Dec 16, 2014 at 9:46 p.m. ET
Image: 20th Century Fox

In his last onscreen movie appearance, Robin Williams brings the laughter one last time, injecting the Night at the Museum franchise with joy and class. Knowing that the comedy legend is no longer with us, however, made for an emotional roller coaster while watching the film.

In Night at the Museum: Secret of the Tomb, Robin Williams reprised his role as America's 26th president, Teddy Roosevelt, once again providing friendship and some fatherly advice to museum guard, Larry Daley (Ben Stiller).

More: Robin Williams' son Zak finally opens up about life without his dad

When Robin first appeared onscreen as Teddy in Secret of the Tomb, our hearts lifted, only to be struck down by the memory that Robin Williams had passed before his time. Way before his time. Seeing him play this role with exuberance and wit was bittersweet. He seemed so in his element, so happy, so primed to keep going.

Night at the Museum

The tears came but soon left because that little capuchin monkey, Dexter, is so darn cute and hilarious, there's no way to cry when he's on the screen. But it was towards the end of the film that Williams' haunting lines of dialogue sent us into full sobs.

More: 7 Things to know about Lewy body dementia and Robin Williams' death

We don't want to give too much away, but there is a point in the film where the magical Egyptian tablet that allows for the statues to come to life may need to stay at the London Natural History Museum — for good.

So, the statues of Teddy, Sacajawea (Mizuo Peck), Atilla (Patrick Gallagher), Octavius (Steve Coogan) and Jedediah (Owen Wilson) have to choose to stay in London or return to New York without the tablet. Much to Larry's surprise, they want to return to New York. Here's the haunting dialogue:

Larry: "If you guys go back [to New York], you won't be alive after tonight."

Jebediah: "We're museum exhibits. It's what we are. Folks come to look at us, maybe learn a little something."

Larry: "But I'm supposed to take care of you guys."

Teddy: "You have. It's OK, Lawrence. We're ready."

We can only imagine how these lines must haunt the filmmakers. One thing we know for sure is that Robin Williams will be missed.

More: Zelda Williams keeps a memory of her dad on her at all times (PHOTOS)

Night at the Museum: Secret of the Tomb is dedicated not only to Williams, but also to Mickey Rooney, who played Gus and also passed away earlier this year. The movie opens Dec. 19.