Then she said the faithful words: "We're working on something."
Puth immediately said he wanted to be involved and would do the music for whatever the "something" is.
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He also egged DeGeneres on about singing the new theme song, but she quickly changed the subject and asked if it was a new movie.
However, Aniston sarcastically replied it was a "huge, huge, huge movie ... no."
"I don't know yet ... I don't want to lead people on."
But DeGeneres didn't want to give up on what the "something" and asked why she posted a photo of the gang on Instagram.
"We did that because we miss each other, and we all happened to be in the same part of the world," the 50-year-old said.
When Aniston joined Instagram, her profile soon went viral after she posted a photo of the full cast.
She ended up breaking Instagram and a Guinness World Record for gathering the most followers in a record time.