After donning a plus-size granny suit in the $118 million-grossing smash Big Momma's House, Martin Lawrence realized there was only one thing left for him to do: Go back in time. And in his latest pic, Black Knight (opening Wednesday), he does just that. "I love fish-out-of-water themes," he tells TV Guide Online, "and what's a bigger fish-out-of-water than a brother from modern day going back into medieval England?"

The 36-year-old comic-actor admits he too was a bit out of his element on the set of the comedy — particularly during the swordplay sequences. "I didn't know how to work a sword or how you fight with a sword," he confesses. "I'm good with a baseball bat.

"But it was fun to play and showboat a little bit, especially since you know you're not really getting hit out there," he adds. "When things get dangerous, they yell, 'Cut!'"

Lawrence also was thrown by the archaic plumbing. "The bathrooms back then were certainly different," he chuckles. "I'm too modern for that life. I like real toilet paper — that straw thing don't work for me. I also like to plug things in and have a light turn on. I can't be waiting for someone to come to me with a bucket of lighter fluid."

With the nation currently in the throes of Harry Potter hysteria, Black Knight faces an uphill battle getting the attention of moviegoers over the Thanksgiving holiday. But Lawrence feels strongly that what the world needs now is some mindless entertainment. "Laughter is the key to massaging our souls," he says. "I think we have to be able to have a sense of humor with each other, because if [we don't], all that built-up tension could be exorcized in the wrong way, and we don't want that. We always need to find time to laugh."