It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

Anyone know all of the cameo locations?

So far I have Caleb in the Cemetary.

Lo Wang in Antarctica Anomaly.
Serious Sam is in Atsui (first map of Egypt)

Duke Nukem is in Masochistic Metropolis (third map of the city)

Doomguy is in Gauntlet (ninth map of Hell)

Ranger/Quakeguy is in the final boss area.
Cant remember well but caleb from Blood is on the first episode, on the medieval zone.