Watch on Deadline

Its pretty wild.

I was like, oh, Ill sit through it.

Itll be so fun.

Maisy Stella and Aubrey Plaza in ‘My Old Ass’

Maisy Stella and Aubrey Plaza in ‘My Old Ass’Shane Mahood/Amazon MGM Studios

It had been a while since Id seen that.

It can really cut through.

I dont do it that way.

Vic Michaelis and Anna Garcia in ‘Very Important People’

I just think about it for a long time, figure out the people.

Its very cathartic for me.

And then I open Final Draft and just start with page one.

I really wanted to walk the line and just keep it grounded.

Ive never done this before.

When I started, I started with the title page.

It was like, OK, I know its calledMy Old Ass.

But here we are, and actually the title has stayed the same, which is incredible.

The mushrooms felt like such an authentic way into a really silly, crazy buy-in.

I really was like, oh yeah, 18-year-olds in Canada going camping would 100% do mushrooms.

It wasnt so magical that it wasnt believable, but at the same time, obviously its not believable.

It just made sense to me in terms of walking that line.

DEADLINE: One of the key things about this film and aboutThe Falloutwas that they were not didactic.

I think theres a little bit of frustration on that side of it.

Would you say it like that?

How does that feel for you?

Do you feel comfortable?

Thats just not usually the case, truthfully.

Its both of their stories.

And I certainly can relate to parts of Elliot, but relate more to Older Ass.

DEADLINE: Maisy was great inNashvilleand I know she wrote a song forThe Fallout.

Tell me about casting her in this?

I didnt know her fromNashville.

I knew her from the Call Your Girlfriend singing video with her sister (Lennon Stella).

Thats how it all started, evenNashville.

I hadnt really seenNashville, I just remember from that video.

DEADLINE: Its great that you took a chance and gave her the lead.

It really paid off.

Luckily, I had producers too.

I mean, she just killed it so unbelievably hard, and I cant believe its her first movie.

Its so unreal to me.

And she hasnt acted sinceNashville, which is also insane.

DEADLINE: Tell me a little bit about working with LuckyChap.

What are some of the ways they supported your vision?

And thats why Ive been holding them so close and theyre such good people.

And after three years when you never see a crack, you know its the real deal.

Theyre just so classy and so smart and so consistent.

And she was the one that was like, do you have any other ideas?

And the only thing I had was this idea of younger and older version meeting.

It didnt have the mushrooms yet.

And then theyre so involved.

They were on set.

Tom (Ackerley) and Margot (Robbie) were there the entire time and at the monitors.

I feel very, very lucky.

DEADLINE: How did you connect to Aubrey Plaza for the role of Older Elliott?

And once we cast Maisy, it was like, OK, who looks the most like her?

Side-by-side putting all these pictures next to each other.

And it was really hard to figure out who that person was going to be.

And we were really stuck on it.

Im a huge fan of her, and I knew Maisy was a huge fan of hers as well.

But, for some reason, her energy was so similar to Maisy in this indescribable way.

The fact that the movies calledMy Old Assand shes not even 40 was funnier to me.

I was like, I dont care if they dont look alike, its a buy-in.

Ill write some jokes about how they look nothing alike.

And then hopefully their energy is so great together that everyone will just get over it.

DEADLINE: You shot on location in Canada on the lake.

How was that experience?

Its unmatched anywhere else on the planet.

I went there every summer as a kid.

I went to a summer camp that was on an island up there.

Wed boat to dinners on the weekend together [on the shoot].

It set the tone for the movie.

DEADLINE: Whats it been like to see all these deeply emotional reactions to the film?

That seems to really be a big feeling.

You just dont know.

I think I have an idea, but things change so much.

Old men lose their st.

They cry so much.

DEADLINE: What can you say about the TV show and the next movie that youre making with them?

The movie is very different.

Its got a music and movement element to it, but its not a musical.

And its very different.

Im excited about it.

Its a big swing.

DEADLINE: What about the TV show?

I dont think Im allowed to say anything about that, but again, its with Lucky Chap.

My Old Assis in theaters from September 13.