Jill crosses her arms when she says, " I should just try dating a geek too." The next shot of her shows her with her arms uncrossed.
When Chandler says "boy did we make friends with the wrong sister," a crew member is clearly visible on the left edge of the screen holding equipment with many yellow wires coming down behind Matthew Perry and the kitchen table.
Monica says that she hasn't been sick in three and a half years, however the last time she was ill was in the fourth season.
Jill says she memorized her father's credit card numbers years ago. To purchase items with credit cards, the retailers need to see the actual card including identification. She wouldn't be able to purchase anything by verbally telling the retailer the credit card numbers. An exception to this would be department store specific credit cards. At some major department stores a purchase can be charged to a customer's department store card by just providing the account number.