The Knocked Up screenwriter and director agreed to answer questions sent in by young female readers in a short film for Rookiemag.com's Ask a Grown Man blog spot.
He first responds to an overweight student who asks if she needs to go on a diet or change her personality to snag a boyfriend.
Apatow says, "Here's the thing, you should never change yourself under any circumstances. Because you'll always be you, but you'll be you acting crazy, trying to act like somebody else. So that's not gonna work! You're perfect the way your are."
Another teen asks for tips on how to kiss her crush and the funnyman says, "I don't know how to kiss a guy - I think you might be asking the wrong person. I think you just do it and it might be in your genes - your genetic code - so maybe trust evolution."
A 17 year old wonders whether she should date a male friend she isn't physically attracted to, but Apatow insists, "If it ain't happening, it ain't happening. You can't make it happen if you're not feeling it."
He adds, "It's sad... These heartbreaks happen. I've had 900 women in my life tell me they're not feeling it, but once a woman said she was feeling it, and (now) she's my wife. She's been with me for 17 years."
Actors Jon Hamm and Paul Rudd have also filmed installments for the Ask a Grown Man series.