Take it from someone who recently tried bringing up Paula Abdul's "Rush, Rush" video to Keanu Reeves: No matter how ill-advised their previous projects might be, no matter how high their careers have since soared, most celebrities avoid bad-mouthing their back catalog.

On April 18, "Forgetting Sarah Marshall" will hit theaters, with Judd Apatow's comedy clan eager to follow in the footsteps of "Superbad" and "Knocked Up." But as advance screenings have built buzz for the flick, a question is on the minds of those who've glimpsed one eyebrow-raising scene: Is Kristen Bell making fun of her last movie?

In August 2006, the actress starred in "Pulse," a horror film about a demon-infested wireless signal that vanished quickly from theaters and currently stands at a lowly 12 percent approval rating on RottenTomatoes.com. In "Marshall," Bell plays a TV actress whose boyfriend teases her about having starred in a movie "with a ridiculous premise: What would happen if your mobile phone killed you?" Meanwhile, her ex jokes, "Why couldn't you just take the battery out of the phone?"

Now, Bell and her gang have shared the scene with MTV News — and they also filled us in on the stranger-than-fiction truth behind it.

"Oh my gosh, I'll give you the exclusive on this," Bell laughed recently, knowing that fans on the MTV Movies Blog have already begun asking the "Pulse" question. "It's too funny."

"She had an interesting reaction when she saw that in the script," said "Marshall" co-star Jason Segel, who wrote the movie with director Nick Stoller. "Kristen was convinced that we were intentionally trying to make fun of her."

"We had no idea that she had done a movie that had the premise of a killer cell phone," Stoller agreed. "We just thought it was a funny idea that seemed in line with all these Japanese horror remakes. And so it came out totally randomly."

Sure enough, "Pulse" was a remake of the 2001 Japanese film "Kairo."

"I hate to say it, but we were trying to think of the dumbest concept for a movie," Segel chuckled. "And that's what we stumbled upon."

Since Apatow's comedies are largely improvised, Bell wasn't aware of the intended joke until just moments before the cameras began rolling; immediately, she suspected foul play. "I just looked at Nick and Jason and rolled my eyes, and they were like, 'What? Isn't that funny?' " Bell remembered. "And I was like, 'You guys, I just don't want anyone to be offended. I don't want to make fun of something that's real.' And they were like, 'What are you talking about?' "

Stoller backed up Bell's story. "She was like, 'Really? Are you gonna go there?' Kristen was like, 'I hope the producer doesn't kill me for this.' "

"Neither of them have seen 'Pulse,' " the actress insisted. "And I know this, because I bugged them about it for a week. I was like, 'You guys, I don't want to offend anyone.' I was grateful for that break. I loved it. It wasn't the best horror movie of all time, but it wasn't the worst horror movie of all time."

Suddenly, Bell sounded again like Sarah Marshall, who defends her film by saying: "It's not for everyone ... it's a metaphor for addiction to technology."

To which her boyfriend (Russell Brand) responds: "It's a metaphor for a crap movie!"

"Part of what's great about working on these Judd movies is that we all bring a bit of ourselves to our characters," observed Segel, pointing out that Bell's character also expresses career concerns after her TV show is canceled (um, "Veronica Mars"?). "Kristen had an amazing tightrope to walk, and she did it. ... That's part of why the movie works."

"If they were really making fun of 'Pulse,' I would have said, 'This is too close to home,' but I was so enamored with the simple fact that they had come up with it on their own," Bell marveled. "It's so weird."

Check out everything we've got on "Forgetting Sarah Marshall."

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