First, allow me to apologize for the lateness of this review. My life has been undergoing some significant upheaval in the last little while, on top of midterms, no less. Thank you to Alice for her patience with me. I just touched on the main points that stood out to me in this episode, apologies for the shortness of the review as well. I promise next week, when life has stabilized again, I'll make a more decent contribution to this fantastic site.
Okay, let's dissect this episode:
Thoughts on "I Believe the Children Are Our Future"
We're back to SOP this week: set up with the teaser and then onto the fake badges and agents to match. Right away, the first thing I notice is that our boys are totally back in sync. Unlike Fallen Idols in which I thought the characterizations were off despite the return to the original formula, Sam and Dean are jiving in all the right ways this time around. The prankster, ribbing, brotherly chemistry was felt in I Believe more than it has been in a long, long time. Several times in this episode were reminders of days gone by: such as when Dean showed Sam his hairy palm and proceeded to grin devilishly when Sam warned against using his razor to correct the palm in question. Everything feels much less tense than it did only a few weeks ago. The strain of unspoken accusations, guilt and grief doesn't hang so heavily over every conversation.

           Grey and dismal was the atmosphere for most of the episode and it facilitated the emotions behind the storyline. The use of childhood myths (lies seems a bit harsh of a word, I don't think of Santa Claus and the Tooth Fairy as a lie but rather a wonderful preservation of childhood innocence) in such a ghoulish way was quite enjoyable. It brought a deliciously creep element to the storyline. I admit, the Tooth Fairy freaked me out. I'm with that little girl - keep your quarters! Enjoyed that Dean was the one to figure out what was happening when talking to Jesse. That was a refreshing change of pace. Usually, Sam figures out what is happening.( And please, don't take that to mean I'm anti-one brother or another, it's simply an observation on pattern).  
The episode was good mix of macabre humour with a rather poignant storyline. All of the gags worked for me but a few stood out:
-          Sam and Dean interrogating the gag-store owner and liquefying the rubber chicken. That was simply awesome.
-          Sam's face when Dean hit him with the joy buzzer and his subsequent pouting as they left the house
-          The whoopee cushion and Castiel: while I normally find the whoopee cushion to be crass and not terribly humorous - this scene rocked. Largely as it was in the middle of a rather dramatic, heady scene, because Misha played it straight without so much as twitching - “that was not me” - and of course, Sam's totally irritated expression. (Can't you just imagine the bloopers derived from this?)
Cas seems to be largely reacting every time we encounter him - reacting to fear, that is. He still has the penchant for adopting a black and white view of the world and now it's combined with fear and a pervading desire to restore the balance of the universe to it's pre-Apocalypse scale. Jesse's existence threatens to throw more powder into Lucifer's already well stocked keg and Cas wanted to stop that before it could happen. As Cas stood with the knife over Jesse, he seemed to genuinely regret was he was about to do, but felt he was serving the greater good with his actions. I think poor Cas is just very confused.
Castiel wasn't in this episode much, but his raison d'tre this week served as a great vehicle to demonstrate the brother's newly regain unity. They were equally appalled by his suggestion that Jesse needed to be killed and seamlessly worked together when it came to talking to Jesse about the fact that he was a half demon spawn. Sam's speech to Jesse very much struck me here. This Sam has come a long way from the soldier who mandated the life of a hunter to little bro Adam only a short year or so ago. Overall, I was impressed with their appeal to the human part of Jesse and the gentle way they approached the whole mess. Our boys are growing up.
What really surprised me about this episode was the character of Jesse. I actually enjoyed the acting and the characterization. Normally, I find child actors aren't very good - they are either written younger than they look/are or with an obscene level of genius and analytical skills that renders them not only unbelievable, but also unlikable. Supernatural has historically had a fairly decent track record with the child characters - but I especially enjoyed Jesse. What worked was that we knew he was powerful but he didn't act powerful - no maniacal cackling and summoning lightening, no electric energy flaring up and crackling around him - he didn't even really raise his voice. I enjoyed the quiet power of this character - much the same way Lucifer's subtleness is appreciated every time he's on screen. Jesse also connected - I felt bad for him, his predicament was a difficult one. (Although, how awesome would it be to have those kinds of powers? I want, therefore it is? Yes, please!) I was glad to have the anti-Christ mythology established firmly in this episode. There has been a pervading theory that Sam was the anti-Christ for a long time and though I believe that was largely dispelled by the Sam-is-Lucifer's-vessel reveal, I was curious about the role of the antichrist in Supernatural mythology all the same.
The end was very touching on a few levels. Jesse's decision was necessary, despite the sadness of it. The note on the bed to his parents was particularly touching and I am glad that the door has been left open for him to return later. Finally seeing Sam and Dean back together in the Impala without all the tension was thrilling but the gentle lament over their loss of innocence at such a young age was sadly sobering.
All in all, I thoroughly enjoyed this episode. To borrow from a Winchester:
"That'll do, pig!"