In answer to the question about Bert having a counterpart on The Muppet Show, I think it is worth mentioning that both Bert and Ernie have showed up twice on The Muppet Show themselves. I can kind of see the similarities with Ernie and Lew though I'd never really thought much about it before.
However, I think a pretty close counterpart for Bert on The Muppet Show would be Sam the American Eagle.
See the similarity?
It's probably not exact, but both Sam and Bert are the more stern (at times) ones who like order and neatness and propriety and get frustrated with the antics of Ernie and Lew or Crazy Harry or Animal, etc. At least that's the closest one I can think of.
As far as Beaker goes, I think "Meep Meep" (like the Road Runner!) IS his language. Apparently, Bunsen is the best at interpreting it, although the others obviously can too. And Beaker has sung "Feelings" before, just as a point of interest, though interpreted into his own language. Beaker has his "meep meep" language just as The Swedish Chef has his "Mock Swedish" language and Animal has his "animal growls interspersed with English words" language. And Zoot has his "half-mumble, occasional intelligent conversation" language.
And the only other frog I know of that sings and dances (besides Kermit, Robin and any of the Frog Chorus, etc.) is Michigan J. Frog (the cartoon frog from Looney Tunes who only sings for certain people!)
Rowlf showed up with Kermit in the pitch for Sesame Street, as well as in the #9 in the "Falling Baker" sketches. So technically, Rowlf was a Sesame Street character along with Kermit before they both became characters on The Muppet Show. Another sort of crossover character from The Muppet Show would be Gladys the Cow. I'm sure some of the penguins and chickens and things that have showed up on Sesame Street are some of the same ones used on The Muppet Show. And don't forget that Beautiful Day Monster showed up in the first season of Sesame Street as well before going on to show up in The Muppet Show.
And on the other end, Sesame Street characters have also shown up on The Muppet Show, the most obvious being Kermit the Frog. In at least three episodes, different Sesame Street characters show up. I know Bert and Ernie are in the 2nd. episode with Connie Stevens. Big Bird shows up in the 3rd. season Leslie Uggams episode and a bunch of characters (including The Count, Cookie Monster, Prairie Dawn, Grover, Bert and Ernie) show up in the 5th. season Marty Feldman episode.
Now I've got one other question. Can anyone tell me on what episode of Muppet Babies that a live action picture of Oscar showed up and if they were any other Sesame Street references (or Fraggle Rock or other Henson production, for that matter)? Also, can anyone tell me if they were any other apperances or mentions or references to any other Muppets on Muppet Babies? I know Kermit, Miss Piggy, Scooter, Skeeter, Fozzie, Gonzo, Animal and Rowlf all showed up, as well as Nanny, Robin, Statler, Waldorf and Janice. Can anyone tell me the specific episodes that Janice and Statler and Waldorf showed up? Also, when was a picture of Miss Piggy seen on Sesame Street?
(I know there was a Sesame Street News Flash skit with Kermit reporting about Old MacDonald's farm, which incidentally had the Yip Yip aliens showing up, and Kermit mentions to a pig that she reminds him of someone he knows- a pretty funny reference to Miss Piggy!
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