"The Count Orders a Hot Dog" is a sketch that originally aired during Sesame Street episode 0714 (i.e. during the sixth season), on January 9, 1975 (although technically, it was created during and for the fifth season, in 1973).
The sketch featured Grover the waiter working at Charlie's Restaurant. The Count, who is sitting at one of the tables, orders a hot dog. When Grover brings the hot dog to the Count, instead of eating it, he counts it and orders another one. Grover, being slightly confused, brings him another hot dog only to have the Count do the same. After the third time, Grover refuses to bring him more if he was only going to count them. The Count then uses a hypnotism spell to bring him more. After Grover grants his request, the clip goes into fast motion along with fast-pace music as Grover brings the Count more and more hot dogs, with thunder sounding each time the Count counts one. The pile of hot dogs keeps growing until Grover eventually falls to the ground due to exhaustion.
There are no copies or screenshots of this sketch available online, although, an (apparently incomplete) fan transcription of the sketch has been made available. The sketch may have been removed from rotation due to parents finding hypnotism or Grover falling down inappropriate for their children.
According to a user on the MuppetCentral forums, the clip made reruns into the 1980's, but it has apparently never been aired since. The forum thread is quite old, (the first post taking place in August of 2003) but has recently been bumped by several users in 2011, and in 2013.
UPDATE 20 June '15: Scarecroe just uploaded of a screenshot of the sketch on Muppet Wiki today while gathering images for Sesame Street episode 1195 (ie. during the tenth season) (originally aired on December 8, 1978) which included this sketch for an episode guide. And good news as if wouldn't you know it, MarshalGrover (known as Oscarfan on Muppet Wiki) has finally uploaded a video of the sketch on YouTube recently today. Hallelujah for those Muppet fans who were always wanting to watch this sketch.
UPDATE 5 June '17: PumpkinJFriend has uploaded a cleaner copy of the sketch that is audio-synced from the German dub, without the timecode in that video source, hence featuring a longer ending.