How exactly do you do an internet search on just a picture if you don't know what it's called? Google "giant walking robot thing"? Methinks it may be more trouble than it's worth to narrow it down, considering we're talking about a Facebook comment, not a PHD thesis.
That and I don't think ignorance of fiction is really dire enough to qualify as "making an ass of oneself". I know you're a massive Star Wars fangirl, but believe it or not, it's not exactly vital information for one's day to day life.
