I'm from California, and I drive a 2002 Subaru Forester.
Today I was getting out of my car when I realized that I left the window open. I put the keys back in to close the window, then got distracted by my friends and stupidly left the keys in the ignition in on.

I came back around 2 hours later to find the keys stuck in the ignition (luckily I had left the door unlocked). I'm pretty sure the battery is dead, and I can't turn the key back to the 0 position because it makes a clicking noise. I'm not sure if it's the alarm or not. So I have to leave the key in 2, but no matter what I do the key won't come out.

Somebody told me the transmission is locked, but I don't know what that means. But I would greatly appreciate if anybody could tell me how to make it so that my key can just come out. Then from there I can just borrow a jumper cable and restart the car.

I'm desperate and have no idea what to do so any help is appreciated. Thank you!

Remove and charge the battery. Many auto parts stores will do this for free. Don't jump the car, since you increase the chances that a voltage spike could wipe out the ECM, alternator, or important sensors. Disconnect the negative battery cable first and reconnect it last. Record any radio codes, prior to disconnecting the battery.

You may want to give the Subaru service department a quick call and explain the situation to them.

But can I do that even though my keys won't come out? So I'd have to get it towed to an autoparts shop..

Personally, I'd call the local Subaru dealer and ask them the best course of action. With security systems being what they are these days, it's the safest course of action. I'm just recommending that it's best not to jump the car, because of the potential to damage electronics.

Some Honda automatic transmissions have a release, where, in case of system malfunction, the shift lever can be released by pushing a key into the release slot near the shift lever.

Did you try depressing the brake pedal for 5 seconds? The link below may give you some insight on automatic transmission interlock systems:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post258005

I got it! Basically just let a car-savvy guy who happened to be in the parking lot take care of it. He used some jumper cables and worked his magic and it eventually worked. The alarm wouldn't stop going off in the middle, but it's all good now!

Thank you for your help :)