Last replacement opponent who beat the bonafide champs

[FinitoxDinamita]

List some fights where the last minute replacement scores upset

[Gentblue]

Indongo????

[Redd Foxx]

Don't know, but I can tell you that everyone who tried promised to, "shock the world".

[Vasyl’s dad]

Manny vs Ledwaba.

[HarvardBlue]

Josesito Lopez replaced Berto when he fought Ortiz. I don't know if Ortiz was a champion but he was expected to win against Lopez. Didn't quite work out that way.
Edit: Lopez's reward was replacing Paul Williams against Canelo. That one didn't work out for him.