Jake Gyllenhaal and Peter Sarsgaard Lived Together During Jarhead Filming  11/14/05

Jarhead co-stars Jake Gyllenhaal and Peter Sarsgaard were so keen to make the movie a success they moved in together during filming.

Sarsgaard, who is dating Gyllenhaal's sister Maggie, was determined to recreate their onscreen reality at home - and he also hoped the move would stop him pining for his lover.

But the 33-year-old star quickly regretted his rash decision.

He explains, "I figured if I couldn't be around my girlfriend, I would settle for her brother. The idea was to simulate the military experience. What happens if you're forced to be with someone every minute of the day and night."

"And we fought. We'd have a fight and then we'd still have to be together.

For a while, I would just wear headphones. All the time. That lasted for 10 days."