Jason Kravits

Sheldon wants to experiment on Howard's kids.

Sheldon is determined to be proved right when a NASA official comes to school and dismisses one of his scientific suggestions.

Ross has a hard time dealing with Rachel's decision to move to Paris whilst Phoebe and Joey pack Monica and Chandler's belongings as the couple accompany Erica, who has gone into labour, to the hospital.

Ross and Phoebe race to the airport to tell Rachel of his feelings. Erica gives birth to twins Jack and Erica and the friends turn in their apartment keys and go out together for one last coffee at Central Perk.

Derek's mother arrives in Seattle and meets Meredith for the first time; the patient on death row wants to donate his organs to Bailey's young patient, Jackson; Callie has a patient who had surgery to make him taller, only it caused massive infections in his legs; Owen asks Cristina out on a date.

Jim backs out of having a vasectomy but is unable to admit he could not go through with it to Cheryl.