Sheldon tells Amy he would wear a pair of shorts because it's 78° outside, but he doesn't have any. He wore shorts when he went jogging with Penny in S4 E2, The Cruciferous Vegetable Amplification.
As penitence for reading her diary, Leonard wears the orange lingerie he bought for Penny that she hates. The lingerie he wears fits his body, which means it would be way too big for Penny.
Penny can't get into Leonard's tablet, because she doesn't know his birthday, however, in Season One-Episode 16, Penny throws a birthday party, because she did Leonard's astrological chart.
Penny thought she knew it, therefore she just forgot the exact date.
Penny thought she knew it, therefore she just forgot the exact date.