The phenomena was popularised by John and Hank Green over at
www.youtube.com/vlogbrothers. Basically adding "In My Pants" to the end of Book titles and Movie titles makes them funnier and more entertaining.
Alan "fallofautumndistro" on Youtube made a rather beautiful discovery, adding in my pants to song titles- in particular Nirvana songs.
So I had some fun with this discovery :)
She Moves In Her Own Way in my pants (The Kooks)
She Will Be Loved in my pants (Maroon 5)
Fans in my pants ( Kings of Leon)
Raindrops in my pants (Regina Spektor)
Safe and Sound in my pants (Azure Ray)
Do You Remember the Fisrt Time in my pants (Pulp)
Take a Chance on Me in my pants (ABBA)
Try Again in my pants (Aliyah)
He Wasn't There in my Pants (Lily Allen)
Everyone's At It in my Pants (Lily Allen)
That Girl in my Pants (McFly)
Cedric in my Pants (The Moaning Myrtles)
Jenny Don't be Hasty in my pants (Paolo Nutini)
Kisses and Cake in my Pants (John Powell)
Play in my pants (Kate Nash)
I Want You Back in my pants (The Kooks)
One Last Time in my/your pants (The Kooks)
Littlest Things in your pants (Lily Allen)
The Trip into your pants (Paperplain)
Draco and Harry in my pants (The Whomping Willows. now who wouldn't like that?)
Ain't No Sunshine when She's Gone from my Pants (Bill Withers)
Reckless in our pants (Tilly and the Wall)
Shy Boy in my pants (Katie Melua)
Me Plus One in my pants (Kasabian)
Double Trouble in my pants ( Harry Potter and the Prisoner of Azkaban)
Seriously, tell me that didn't amuse you. XD