2x10 - Maniac Mansion

Lenny met a girl in France and they are planning to get married. She comes to meet the family, and things go well. Later, Lenny tells Teri he can't marry her because he could die soon. The doctor told him if he gets hit in the head one more time, that would be it. He eventually decides to go through and have the wedding anway. During the ceremony, Lenny drops the ring and he bends down to pick it up. Teri goes to get it at the same time and they bump heads. The collision puts Lenny into a coma, and everyone thinks he's dead.