In episode 6, Natsume and Nyanko sensei find out that Natsume is being possessed. Nkanko sensei nonchalantly exorcises the Youkai by headbutting it. A nearby ayakashi raises a fan with the Japanese flag on it and congratulates him.
The introduction of Hinoe, who like just about everyone before her immediately assumes Natsume is his grandmother when she meets him. Though unlike everyone else, curiously, she greets him with a rather aggressive fondling-session, before she astutely observes:
The forest boy recounts how Reiko described the ocean to him:
Boy: It is blue and infinitely vast... Nyanko-Sensei: Mhm. Boy: There would always be waves and the sunlight and moonlight would sparkle... Hinoe & Nyanko-Sensei: Mhm! Boy: And there's a long necked dinosaur living in it... Hinoe & Nyanko-Sensei: Mhm, mhm! (beat) What?! Boy: And there's an island that is it's hideout and if you're lucky, you can see an UFO taking off... Hinoe & Nyanko-sensei: 0_0 ...
Episode 1 of season four, Natsume is lost in the forest after having been attacked by a group of youkai and is observing a strange set of talismans hung among the trees when Nyanko sensei pops out of nowhere and lands on his head.
Episode six of season four follows Natsume after he's been trapped in a jar by an ayakashi, and Nyanko Sensei's subsequent efforts to free him. Hilarity Ensues.
As well as Nyanko Sensei shapeshifting into Natsume in order to keep people from thinking that he's gone missing. His mannerisms change from Natsume's usual extremely polite to much more relaxed and almost arrogant. Natsume is utterly dismayed. One of his friends is so shocked he thinks that Natsume may be sick for an instant and offers to take him to the nurse's office.
Poor Jun thought that "Natsume" had gone insane and was going to confess to her...then he said she smelled delicious (he was smelling her lunch).
In the first half of The Moon-Splitting Festival arc, the noises Natori and Natsume both make when they discover each other can't get any more disbelieving or shocked.
Episode 11 of shi reveals that Madara also acts as a Head Pet...when he and Natsume are brushing their teeth. He just idly sits there brushing his teeth when on top of Natsume's head.
There's an instance where Natsume and Nyanko-sensei see a commercial featuring Natori at his sparkliest and they laugh to the point of tears.
The final episode of season three features Natsume just playing shadow-tag with his youkai friends, which also doubles as a Crowning Moment of Heartwarming. Nyanko-sensei and Misuzu get really into it, and at one point somebody asks if the winner gets to eat the losers.
Taki's usual reaction Nyanko-sensei, especially in A Broken Mirror when she says want you... in this creepy, seductive voice and grabs him from behind.
Nyanko-sensei waddling away on his belly in The Thing that Lurks in the Storeroom
Many of Nyanko-sensei's nicknames and times that Sensei got drunk.