I agree, quite interesting... although, like ametur_poet suggested, I don't know if Bart would be cunning enough to pull off something as well planned out as that. Or outsmart Lisa like you're suggesting he did Also... if there was a deeper pleasure than making things up with his sister on his smile during that kiss, I'd say it'd go against what we know about Bart. He generally doesn't like Lisa, and is usually disgusted by her. For someone like me, being kissed by Lisa is being sent to cloud nine, however for him... I'm not so sure Still, it's an interesting possibility

Dagdamor
Very interesting theory And I partially agree - he isn't simple boy, sometimes he shows fake feelings and of course he thinks about his own benefit even in sibling relations (remember when he was told about Lisa's future as a President, he knew she may be useful for him). But I must agree with ametur_poet, Bart is not so smart and consecutive to plan it day after day.

But he uses Lisa different way - to show others that he is cool. Very often he hurts Lisa acting that way - in "Secret war of Lisa Simpson", for example. He's afraid to show his real feelings, because others chilren's words are so important for him. Of course, it's kinda normal for 10-years old boy, and I'm so happy, when he is expressing his real deep feelings. I prefer to believe that it's real Bart - kind, vulnerable and loving brother.
But there are a lot of cruel moments in their relations, especially last season. Bart puts Lisa's baby pictures album under his foot to reach gas pedal, Bart says he loves his new pet snake more than Lisa - all these moment are so disappointing :/
These relations like that moment, when he broke his close relations to Marge in "Marge's son poisoning", after jokes from bullies. I think, Bart-Lisa relationship would be much stronger when he'll become older and more independent from other people opinions.

Yes, Janglewolf and Brakusaetsya (most complex nick i ever spelt )'s reasonings are imho what ultimately is true. And so much better from a simple "feelingful" point of view. It was fun for a while to think about possible other insights, though

Dagdamor
Nope, I've said quite opposite: he really loves her, I think, but he is so selfish and childish that he could do something really bad for her. Then he shows his real feelings, but one day it may happen too late...

GeorgeHarrison
Lisa will forgive Bart everything. She can't hold grudge against anyone for more than 22 minutes.
What I'm more worrying about, is that one horrible day Lisa might simply not live long enough to see Bart's next remorse, considering things he does to her - some of them are plain dangerous! I'm not serious here of course, I believe this is not going to happen - the Simpsons is the sitcom show, and every character is important, but still... sometimes I have this weird feeling watching Bart's behavior.

GeorgeHarrison
Of course sitcom rules never let her die or terribly ruin her life. But it comes so damn close sometimes, and even kind and patient Lisa gets angry, so it could ruin their relationship, making a distance between grownups Bart & Lisa, if he wouldn't change his behaviour. Patience has its limits, I think even for Lisa unforgivable things exist. I don't think she would hate him all her life if he'll do something really terrible, but it may change their relations to formal family meetings one time every year.

SimpReal
That's what lead me to make my point about "Maybe this is just a sibling rivalrly like every other family with brothers and sisters", usually they turn out all right when they're adults As long as one party isn't extremely abusive (which they usually aren't), the two usually grow up and forget about their problems.

I think, actually, they would both be able to live in peace if not for Bart. Lisa's general attitude is typically the peaceful one, Bart is usually the instigator in all these situations.

That's a really interesting question, Bra!
Let's see... thinking about it, Lisa has the typical character of a first born. Caring, mature, sensitive, while Bart has all the traits of a second born. Envious, troublemaker, irresponsible and hyperactive. But still we can notice "joining points" in various episodes where Lisa's character deviates a bit into Bart-territory and viceversa.

If they had reversed roles, i think their respective characters would be even less balanced, maybe making for a more unstable relationship and possibly even a worse show altogether.
But maybe.. just maybe... you can never know. Lisa could have grown up more spoiled and Bart more responsible in respect. This is a very thoughtful issue.