History of Middleweight champions fighting on a undercard

Just a bit of trivia
Nonpareil Dempsey(Webber vs Self)
Bob Fitzsimmons(Jackson vs Nolan)
Kid McCoy(Bernard vs Knock)
Tommy Ryan(Pigeon vs Agnew)
Stanley Ketchel(Herrera vs Long)
Billy Papke(Dundee vs Kirkwood)
Frank Klaus(Lewis vs Martin)
George Chip(O'Neill vs Walsh)
Al McCoy(Welsh vs Bloom)
Mike O' Dowd(Gibbons vs ***an)
Johnny Wilson(Herman vs Murphy)
Harry Greb(Dempsey vs Miske)
Tiger Flowers(Brown vs Burns)
Mickey Walker(Davis vs Burns)
Gorilla Jones(Vaccarelli vs Gotch)
Marcel Thil(Ambers vs Montanez)
Ben Jeby(McLarnin vs Brouillard)
Lou Brouillard(Petrone vs Houle)
Vince Dundee(Dundee vs Zivic)
Teddy Yarosz(Rocco vs Perroni)
Babe Risko(Pirrone vs Dukelsky)
Freddie Steele(Carter vs Duffy)
Al Hostak(Matthews vs Sikes)
Solly Krieger(Risko vs McAvoy)
Ceferino Garcia(Ambers vs Montanez)
Ken Overlin(Armstrong vs Chavez)
Tony Zale(Brown vs Celebron)
Billy Soose(Wilson vs Kaplan)
Rocky Graziano(Larkin vs Constantino)
Marcel Cerdan(Brown vs Angelmann)
Randy Turpin(Turpin vs Finch)
Jake LaMotta(Collins vs Cam)
Sugar Ray Robinson(Williams vs Flores)
Bobo Olson(Ortiz vs Castillo)
Carmen Basilio(Yarosz vs Perkins)
Gene Fullmer(Layne vs Whitlock)
Paul Pender(Jenkins vs Vaccari)
Terry Downes(Winstone vs Spinks)
Dick Tiger(Molloy vs Phillips)
Joey Gardiello(Saxton vs Linam)
Nino Benvenuti(Rinaldi vs Calderwood)
Emile Griffith(Mathis vs Chuvalo)
Carlos Monzon(Lemos vs Chetta)
Rodrigo Valdez(Napoles vs Lopez)
Hugo Pastor Corro(Duran vs Castellini)
Alan Minter(Ali vs Spinks)
Vito Antuofermo(Benitez vs Curry)
Marvin Hagler(Leonard vs Benitez)
Sugar Ray Leonard(Norton vs Young)
Tommy Hearns(Hamed vs Ingle)
Iran Barkley(Jones Jr vs Harris)
Roberto Duran(Tyson vs Ruddock)
Frank Tate(Whitaker vs Chavez Sr)
Michael Nunn(Morales vs Torres)
James Toney(Morrison vs Bentt)
Roy Jones Jr(Bowe vs Ferguson)
Doug DeWitt(Holmes vs Mercer)
Nigel Benn(McCall vs Bruno)
Mike McCallum(Benn vs McClellan)
Reggie Johnson(Hearns vs Delgado)
Chris Eubank(Hamed vs Vasquez)
Julian Jackson(Duran vs Morales)
Quincy Taylor(Tyson vs McNeeley)
Keith Holmes(Holyfield vs Toney)
Gerald McClellan(Lewis vs Tucker)
Chris Pyatt(Benn vs Collins)
Steve Collins(Pyatt vs Cameron)
Lonnie Bradley(Holyfield vs Tyson 2)
Jorge Castro(Weaver vs Brown)
John David Jackson(Lewis vs Jackson)
Otis Grant(Ouellet vs Bonnamie)
Bernard Hopkins(Brown vs Pettway)
Bert Schenk(Lewis vs Klitschko)
Jason Matthews(Eubank vs Calzaghe)
Armand Krajnc(Johnson vs Ullrich)
Harry Simon(Margarito vs Santos)
Hacine Cherifi(Hurtado vs Bailey)
William Joppy(Rahman vs Lewis 2)
Hector Velazco(Narvaez vs Carvalho)
Felix Sturm(Sanders vs Klitschko)
Oscar De La Hoya(Jones Jr vs Toney)
Maselino Masoe(Karmazin vs Spinks)
Jermain Taylor(Jones vs Tarver)
Arthur Abraham(Pacquaio vs Bradley 3)
Kelly Pavlik(Pacquaio vs Mosley)
Sebastian Sylvester(Byrd vs Klitschko)
Sebastian Zbik(Stieglitz vs Gutknecht)
Julio Cesar Chavez Jr(Pacquaio vs Cotto)
Sergio Martinez(Morales vs Barrera)
Marco Antonio Rubio(Pavlik vs Hopkins)
Dmitry Pirog(Marquez vs Diaz 2)
Daniel Geale(Zappavigna vs St Clair)
Darren Barker(Thaxton vs Meager)
Gennady Golovkin(Sturm vs Gevor)
Hassan Ndam NJikam(Joshua vs Ruiz)
Peter Quillin(Garcia vs Judah)
Andy Lee(Froch vs Groves)
David Lemieux(Alvarez vs Khan)
Miguel Cotto(De La Hoya vs Mosley)
Saul Alvarez(Mayweather vs Cotto)
Billy Joe Saunders(Fury vs Chisora 2)
Demetrius Andrade(Corrales vs Machado)
Daniel Jacobs(Malignaggi vs Broner)
Jermall Charlo(Russell Jr vs Gonzalez)
Ryoto Murata(Crawford vs Postol)
Rob Brant(Lomachenko vs Nakatani)
Erislandy Lara(Marquez vs Katsidis)
Zhanibek Alimkhanuly(Porter vs Crawford)