He's baaack -- Episode 302, "Cane and Able"

Clinic patient:
Main patient from season premier.
When we last left off, Cuddy had cured him with House's diagnosis of Addison's disease, and she and Wilson were conspiring to keep it from House to teach him a little humility.

The connection:
The theory floating around this episode is that House has slipped into depression over having "failed" the last case. The depression, in a roundabout way, is causing his leg pain. Compound that with Wilson and Cuddy's lesson in humility, and House is also, as Cameron says, "dismissing symptoms, looking for easy solutions" in the main case. In other words, not being House.

The dismissiveness doesn't come right away, of course. But after House goes through his traditional montage of thinking, in which he usually works past whatever diagnostic hurdle his patients give him, he announces that they should just "send the kid home."

So Cameron -- who treated Addison's guy in the clinic, discovered the humility plan and then made a general nuisance of herself -- runs to a guilt-ridden Cuddy, who runs to House and has the following conversation:

Cuddy: "You're just giving up on this kid?"
House: "You gotta know when to stop."
Cuddy: "You don't stop. You never stop. You just keep on going until you come up with something so insane that it's usually right."
House: "Except on my last case."
Cuddy: "Don't be pathetic. Forget the last case. ..."

House rattles off some crazy ideas about chopping off limbs and such, and Cuddy basically says OK -- "I just want you to do something." House calls her out on The Plan and Cuddy confesses.

House: (speaking to Cuddy's stomach) "Oh, your mommy is in such trouble. Such a liar! That's why you don't have a daddy. That's why she had to ..."

... use in-vitro fertilization, which the kid's mom also did, which led House to the diagnosis of chimerism.

So the coverup of Addison's guy hindered the kid's chances, and the revelation helped him. The question, I suppose, is whether Cuddy's admission cleared House's head enough that he was able to stumble on the solution, or whether he would have come upon it anyway. Whatever the case, he at least returned to extremes to induce the kid's hallucinations so they could cure him. House is back.

Etc.
Addison's guy: "I want to have sex with my wife, and I was hoping maybe you could ..."
Cameron: "Viagra. You're here for Viagra?"
Addison's guy: "A bucketful would be nice."
Bless him.

-- House mentioned the "X Files," but if he watched "CSI" -- specifically the finale of Season 4, "Bloodlines" -- he would have had his diagnosis about halfway through the episode. I'm just saying.