These are plaid sleep pants based on Beosboxboy's Shirtless pajamas. You will need to download the mesh in order for these to appear in your game. They can be found here:
http://www.insimenator.org/showthread.php?t=3719I searched everywhere to find these type of pants, but couldn't find any, so decided to attempt them myself. This is my first bodyshop project, so I'm sure they're not the greatest, but I *think* they came out well enough to post. There are 8 colors in the Rar file. I hope you like them.
A huge thank you to Beosboxboy for creating the original.