From a forum on Alien-UFOs.com: "Alien existence can't be proven, until one lands somewhere and a little grey/green/lizard with polkadots come out of their craft/ bucket or interdimensional porthole from never never mars.
From some guy's dream: "Everybody was filing into these interdimensional portholes, and a lot of people were having large polite 'end of the world' parties in houses abandoned by the rich before they went over themselves."
From a debate on the Bermuda Triangle on AboveTopSecret.com: "True, many ships and planes have been lost within its boundaries over the centuries, but the idea that the area had paranormal hazards did not become part of its legendary status until the late 60s and early 70s, when a series of stories and books began to promote the idea that ships within it were being snatched away by either aliens or due to an "interdimensional porthole.'"
From a review of some artist Phillip Bottenberg's paintings: "Balance is very important to me," Bottenberg says of his ethereal abstract oils, a similar blending of cloud and colour into ultimate equilibrium - paintings that come across like interdimensional portholes, storms of ghosts, held together under a thick glaze (and no doubt candy to glazed eyes). "Ghosts and glaze have a connection actually," Bottenberg says through a flurry of historical references. "The way I'm painting now has a connection with an Italian expression, pentimento, which means "ghost image."
From a description of a game featuring the Transformers robots: "The gameplay is made exciting by the invasion of alien monsters called the Skriix. The Skriix arrive through an interdimensional porthole and lay waste to all they encounter."
From a discussion board for people with ADD: "I think there is an interdimensional porthole somewhere underneath all the clutter where all the trash we throw out gets booted back in."
I think I like the "porthole" imagery rather than just plain "window." The porthole implies traveling, as on a ship.