I noticed ECC has been kind of dead as of late, so I thought I'd try to liven things up again with an observation I've had:
There's a couple of mild similarities between Brain and Cookie Monster: for one thing, both of them started out with "the" as part of their names, particularly in the earlier episodes of their respective series, which was later dropped ("THE Brain" and "THE Cookie Monster"). Also, there were a few little unusual traits of their characters that were later dropped as well; for example, although Brain was always the smartest and most intelligent kid in school, he was also something of a big comic book collector, as well as a slob - a couple of traits that seem really unusual for him in hindsight. Similarly, although Cookie Monster always had an insatiable appetite for cookies, he also had a tendancy to eat ANYTHING - even trying to eat other characters.