"Best" is relative, but I guess the most wholesome is when I once forgot to lock the cage properly and went to sleep. One of my rats went straight to the bed and proceeded to cuddle, instead of wrecking havoc. It's not that common for rat girls, but she did it anyway, my little champ. She spent all the night there. It was truly a bonding moment, especially since she was a very small ratto at a time and being a kid she's supposed to rather eat the shit out of everything in the room (since socialization is often based on making them not destroy things with teeth)