Yes, and here I am.
Tear refered to as first or second tear characters, designates their importance in rank. For example... Main core characters would be first tear, fan favorites and well to relatively known obscures would be second tear, and vaguely remembered obscures would be third tear. Kind of the same thing as organizing characters into A-List, B-List, C-List and so on. Trust me, this was much easier to determine with the cast of actors on Saturday Night Live once their cast expanded in the 80's than it is with Sesame Street.
As for classification... You have "main core" as the ones everybody knows and the ones that have to be there to give the line the strength needed. Palisades usually labels these characters the "big guns" or "anchor" figures. Fan favorites are those who, though not ever-present, at least are well known enough to strike a cord of nostalgia with a good chunk of people. Not as much as the main cores, but a good chunk. Obscures basically covers everybody else, from those somewhat known to all the background characters that popped in and out from sketch to sketch.
As for lineup format... The formula used at first with the Muppets figures was to get two anchors, a fan-favorite, and an obscure to help balance out the line, give the line longevity, and to have something that'd appeal to a broad range of consumers. If the public picks up only the fan-favorite, then at least there's something that consumer picked. If it had been all anchors, then Palisades would've had to use a lot of variants come the latter series around 5 and after. Not sure if it'd be wise to use the same formula for formulating wishlists or lineups that Palisades themselves will implement. You know the anchors have to be there, it's just a matter of choosing wisely between the fan favorites and obscures, and seeing where it'd be best to go with which choices.
Hope this helps.