Type O blood

Type O blood was actually meant to be Type Zero blood, due to lack of glycoproteins in the red blood cells. It was misread as type “O”.

I guess you can call it a typo.

4 cigarettes

3 guys are on a boat and they have 4 cigarettes but nothing to light them with. What do they do?

They throw one cigarette off the boat and the whole boat becomes a cigarette lighter.