Joe: Junk food. Lots and lots of junk food. Every time you guys eat junk food, you go a little overboard, making you both feel bad about later.
Murr: Staying in bed with you all day. The only thing that makes him feel guilty is not getting anything done, but he loves cuddling with you all day.
Sal: Karaoke. You guys love going to karaoke bars, but when you wake up hungover the next morning, that's when the guilt starts to kick in.
Q: Country music. You guys never knew why, but you always loved dancing with each other to country music. Both of you are still kind of embarrassed that you listen to country music and hope that your friends don't find out.
