Hey Katie, we’re wondering why you seem to have more fun when you’re on your own?

Now here’s a HollyShocker if we ever heard one: Katie Holmes has been the life of the party at the Sundance Film Festival this week!

“Katie is all over the place in Park City and really coming out of her shell,” a film festival insider tells HollywoodLIfe.com exclusively. “I thought she was snobby and uptight but she’s really very sweet and VERY talkative. At one point I was like ‘Is she ever going to shut up?’”

The 31-year-old actress even let loose and – gasp – had a drink during a private dinner for her film The Extra Man at the Greenhouse Actors Lodge Jan. 25. Katie chatted to co-star Kevin Kline and drank down a Ketel One and Coke cocktail about normal family things like her step-daughter, Bella, finishing high-school in a few weeks and how much she missed reading to 3-year-old Suri while away promoting her film.

So why is Katie suddenly a Chatty Kathy? Every time we’ve seen her with hubby of three years Tom Cruise, 47, lately, she’s appeared quiet, demure and – dare we say – robotic.

Maybe it’s all that temporary freedom that’s making Katie let her hair down, or maybe it’s her new-found friendship with her The Romantics co-stars Anna Paquin and Dianna Agron – which also premiered at the festival.

Whatever it is, we hope this fun Katie is here to stay!