Unfortunately my encounter with the stairs puppet was spoiled a little by a user on here that had an animated gif of that bit in their signature. As soon as I saw the stairs I knew something would run down them.
(When looking at names in the editor, there's both entity name (the file) and instance name. Sometimes the instance name gives more info on who they are. For example, the "puppet_dreamer_male" entity is used 3 times in Theta Exit, one of them has the instance name of "VictimStrohmeier", the others are generic like "mind_coral_victim_alive_1")
Ok, from page 3 list:
#4 is mind coral puppet 2.
#5 is mind coral puppet 1.
If you look at their designs in super secret, they are both made of multiple people of different ethnicity merged together, not a single mutated person. So #5 might be part Akers, but also part of someone else.
#6 is called robot head in the editor (and robot girl in super secret).
Edit: Actually, the map script file uses the term Akers a lot for monster activity in Theta, looks like #5 might be at least partly him. A staff report said "The Proxy we killed was blind, just like Akers. But it listens! Careful -- we spotted two more by the infirmary."