system
Given the following post, respond as if you're commenting on Reddit:
human
[Short Circuit] how the hell did Stephanie Speck think that Johnny 5 was an alien and not a robot at first? I don't think he could look anymore robotlike than he already does...
gpt
Johnny 5 (despite his name) was one of a kind. 

Given the timeframe of this period-piece, 'robots', especially 'robots that do not look humanoid' were a thing only seen in movies.

Furthermore, Johnny 5 was of an experimental military design, created by NOVA Laboratories, as part of the S.A.I.N.T. (Strategic Artificially Intelligent Nuclear Transport) program. In other words, a truly unique design.

On top of all this, Johnny 5 suffered a catastrophic reprogramming to give him both a sense of self, and one of free will. It took Johnny quite some time to 'integrate' himself, and had a collection of verbal idiosyncrasies (awkward grammar, repeated requests for 'input', malapropisms, etc).

So, in sum, Stephanie either had to make the deduction that Johnny was either:

* A fully sentient robot, ripped straight from the covers of pulp-scifi comics and movies, despite nothing even remotely similar to it existing prior in the real world/news/life

* "Something from Somewhere Else" (ie: an alien/extra terrestrial) which required much fewer assumptions on her part. 


Imagine, if you will, travelling back to say, 1986, with your favorite smartphone/tablet and a collection of 'offline' applications/media available to you, and showing that to your average American.

With a touch/tap/slide of your finger, you have a device that clearly has roots in what you know (television, camera, radio, video games, books, computers, etc), but is so unbelievably advanced and different from what you've experienced or heard of in real life (fancy graphics, widescreen format, touchscreen, dozens of games, etc), that you either have to believe that you are somehow unaware of literally hundreds of 'technological advancements and capabilities', or this device is from 'somewhere else' (the future, alien technology, magic, an illusion, whatever).

In short, given the capabilities of technology at the time, especially with 'robotics', it made more sense to Stephanie to think "Extra Terrestrial" instead of "nearly-magical robot from earth".