You are correct, "They're Baaack" is from Poltergeist.
The line which includes "...I'm Baaack!" is from Independence Day.
Randy Quaid says, " Hello Boys, I'm Baaack" just before he flies his
into the alien ship and brings it down.
On Sat, 21 Jul 2001 06:59:03 -0700 Maggie White
> artappeal wrote:
> > >From which movie is, "I'm baack?" I'm thinking of doing a
> bulletin board
> > with all self portraits, entitled,"We're Baack." However, I need
> to know
> > the movie so I know if it's appropriate and/or clever/funny,
> It's from the second Poltergeist movie; I believe the line, "They're
> baaack" was for the advertising.