Best solution is to force the Ramirez inside to go outside with the other Ramirez … and don’t let either of them back inside.

Sorry Ramirez :(

Two courses of action.

1. You detain and tie up the Ramirez already inside, just in case. Then you let the Ramirez outside in and do the same. You proceed trying to figure out what’s going on. Who is the real one? Problem with this scenario is now you 100% have the fake one inside with you.

2. You detain and tie up the Ramirez already inside, just in case. You leave the one outside to die. Unethical, but now there’s only a 50/50 chance the one inside with you is the fake one.

Alternate option if you’re feeling really unethical is you just instantly kill the one already inside and also leave the one outside to die. Technically the safest option.

Red Dwarf - Psirens (1993)

As KRYTEN and LISTER head for the cockpit, the airlock monitor fizzes on again and a SECOND LISTER appears on the screen.

LISTER 2: What the hell are you doing taking off when I’m still outside? Let me in.

KRYTEN double-takes between the LISTER inside and the LISTER on the monitor.

KRYTEN: I’m afraid, sir, you’re already here.

RIMMER steps down from the cockpit.

LISTER 1: He’s a Psiren – don’t let him in. LISTER 2: For god’s sake – I can’t hang on any longer. He’s the Psiren. Let me in! RIMMER: What do we do? KRYTEN: there’s no way to tell which is which. We have to let him in. RIMMER: That means we’ll definitely have one Psiren on board. A brain- sucking psychotic temporal lobe slurper. KRYTEN: There’s a fifty per cent chance we have one on board already. We can’t risk killing the real Lister. I’m letting him in.