When J.D. hands the Janitor a goldfish to hold he'll do his best to make sure it goes unharmed. He may have a rough exterior but we know he's a good guy.
J.D. and Denise look in on their patient, Mr. Fremont, who's dying of lung cancer and leaving behind his wife and eight year old son. Very sad... to humans like J.D. Not to Denise.
Dr. Kelso: You know, you hurt my feelings earlier. Dr. Cox: In my defense, you are a soulless creature from the netherworld who doesn't really have feelings
[Dr. Cox telling Kelso how much he misses him...] Dr. Cox: When you were the Chief, you were a jackass and a nightmare and I hated you a great deal. Dr. Kelso: That's a good start
