Hi:
I have a copy of this Donahue episode on VHS.
I know this for sure, cause it's the 25th anniversary celebration from 1994, and I've watched it MANY times! I don't have the tape on me...It's at my parents' home in Nashville.
They had a mock-up of the Sesame Street set on the stage (a brick wall behind which Muppets could appear from, with Oscar's can in the center, and a bunch of crates surrounding it....And the Sesame Street lamppost at stage right.)
They had most of the Muppet performers of the time and the human cast, Gordon, Luis, Maria, Bob, even Susan (including Ruth Buzzi who was starting that season).
They also mentioned the debut of Zoe that season as well.
A bunch of toddlers and their parents were there (some of the kids even asked questions like: "Where's Cookie Monster?" Donahue said Cookie was at the dentist, but in reality Frank Oz couldn't make it....."Where's Savion?" Savion Glover wasn't there....And the most clever question from a young girl: "Does Big Bird have anything to do with Oscar the Grouch?" meaning, why weren't Oscar and Big Bird on the Donahue stage at the same time? (Carroll Spinney alternated between the Oscar and Big Bird appearances before and after the commercial breaks).
They showed important clips from the shows then-25 year history, including the death of Mr. Hooper, the adoption of Miles,
They had the writers up on stage at one point as well: Norman Stiles, who was head writer at the time, Sonia Manzano.....
And then at the end they had a birthday cake with Happy Birthday Seasme Street printed on it in icing....And Elmo helped lead singing the Happy Birthday song to the show over the end credits.