- Viggo Mortensen (replaced Stuart Townsend in the role of Aragorn in the Lord of the Rings movies)
- Wally West (replaced Barry Allen as The Flash)
- Hector Sebastian (replaced Alfred Hitchcock as the patron of the Three Investigators)
- Ruth Plumly Thompson (replaced L. Frank Baum as author of the Oz books)
- Shoshana Bean (replaced Idina Menzel as Elphaba in the Broadway production of Wicked)
- Sammy Hagar (replaced David Lee Roth as lead singer of Van Halen)
- Draco Malfoy (replaced Terrence Higgs as Seeker on the Syltherin Quidditch team)
- Alyson Hannigan (replaced Riff Regan in the role of Willow Rosenberg in the television series Buffy the Vampire Slayer)
- Natalie Teeger (replaced Sharona Fleming as Adrian Monk's personal assistant on the television series Monk)
- Sargent Shriver (replaced Thomas Eagleton as the 1972 Democratic Vice Presidential nominee)
Today's list is for boliver, who wanted to see Sammy Hagar mentioned in a list. This was a tough list to get started on; I tried an ultimately rejected two other themes (though one of them I'm going to hang onto and rework for another day) before coming up with this one, which was rather entertaining to compile. I'm particularly proud of myself for working in a reference to the Three Investigators, a regrettably out-of-print children's mystery series which I happen to know boliver is particularly fond of.
Interestingly, the seventh entry is itself a replacement. Originally, no. 7 was Lou Gehrig*, who on June 2, 1925, replaced Wally Pipp as the starting first baseman for the New York Yankees, a roster change that marked the first of Gehrig's 2,130 consecutive games. But then I pulled up the user icon that I would be using for this entry (10-M, as I like to call it), I realized I would have put a Harry Potter-themed replacement in the list. I happened to know off the top of my head that Terrence Higgs had been the Slytherin Seeker during Harry's first year at Hogwarts (because one of my employees stumped me with that question the other day when we were playing Harry Potter trivia), so Lou was out and Draco was in. In retrospect, I think it was a weak entry; it would have been better to say that Ellsworth Dahlgren replaced Gehrig. In fact, let's see... nah, I'll stick with this lineup.
* Just to forestall the obvious joke: "No, Gehrig was no. 4!"