Whatever it is that's going on between them - Robert Pattinson and Katy Perry for sure know that in their celluloid world, nothing is ever kept a secret from the public forever. Soon, all the juicy truth will come out.

Are they or aren't they?

It seems that question will have to wait for a while to get an answer as the couple tries to enjoy their "friendship" under wraps. But if things will be based on the tell tale signs, we think it won't be long until people see something developing between the two.

Sources say the two often hang out because they're good friends. Nothing wrong, friends after all can go out on dates - as friends. But why do they hide? Last June 8, they were spotted at Bjork's concert at the Hollywood Palladium in Los Angeles. According to X17Online, the pair arrived at the venue separately but met up inside.

"They had planned to meet up before going inside to the concert. They must have been coordination on their cells phones because they pulled up next to each other in the parking lot, rolled down the windows and were talking. They parked and then met at the door and went inside together," a photographer apparently told the site.

Katy and Robert stayed together throughout the concert, according to reports. But they again left separately in an attempt to avoid the paparazzi. "Katy came out the back door by herself, trying not to be noticed. She was looking around to see if there were any photographers. She definitely didn't want to be shot with Rob," the photographer said.

It is this sneaky attitude that makes the gossipy tongues wag and the imaginations run wilder. If there's nothing there, why not give a categorical statement to squash all fictitious stories once and for all? Come out clean and then enjoy the friendship without inhibition or worry. Katy and Rob can't be hiding all their life, even as friends, right?

The Bjork concert was not the only event that saw the pair keeping it low-key. They were also earlier seen at a Daughter concert and at a wedding rehearsal in Santa Barbara, California. The two, as usual, acted chilled in public allaying speculations of a romance between them.

But the more they try to fight it (and hide), seems that the more their actions betray them. According to a source, the two are now having sleep overs. Rob had allegedly stayed in Katy's L.A. house after they went away to Santa Barbara together. Katy has reportedly introduced Rob to her parents, too.

What's more, there are rumours that the pair are now talking about heading to Bahamas in the next few weeks to visit some friends of Katy. And you know how most Hollywood romances are often confirmed? It's when two people take holiday vacations together.