about " secret pumpkin"

[english-learner]

What does " secret pumpkin" mean here? Thank you!

SAM
That hurts, Billy. Why would I lie to a journalist of all people?

BILLY
Why do you keep looking over my shoulder?

SAM
Why?

BILLY
Yes.

SAM
‘Cause Alger Hiss just walked in with my secret pumpkin.


BILLY
What?

SAM
There’s a woman over there. I think she’s looking at me.

BILLY
Really?

SAM
I don’t know. I never know if they’re looking or not.

Billy turns 180 degrees to see a woman sitting on a couch with a drink. She looks
to see him obviously eying at her. Sam sighs.

BILLY
Yeah, I think she was.

SAM
I want to thank you for the casual way that you did that just now. She probably
didn’t notice that.

[Tdol]

Is it a reference to Cinderella?? Just a guess

[Satoshi Banya]

"secret pumpkin" may refer to the pumpkin in which Whittaker Chambers, a senior editor at Time magazine and a former Communist hid the secret film he allegedly received from Alger Hiss. Alger Hiss was a high ranked officer at the Department of State and later accused of being a Soviet spy.