[The incredibly tall lurking is enough to get Zim's attention, mostly due to the whole tallness thing (seriously, so tall) and the utter lack of a disguise around humans (and non-humans, which for the moment he is conveniently ignoring). Really, the latter just has him offended, given how much work he's put into his own brilliant human disguise.
Not that a wig and contact lenses are actually full of work or brilliant in any way, but anywhoo. Another alien walking around disguiseless is not good for his own undercoverness, so he's going to subtly sneak away from the main crowds to confront this extremely-tall-purple-guy-who-is-not-Tallest-Purple.
He'll get his attention by yelling, because that's sneaky.]
Hey! Heyy! [Look, Goliath even gets a little arm flailing!] What do you think you're doing??
A. Sorry this is a late thing, feel free not to tag!
Not that a wig and contact lenses are actually full of work or brilliant in any way, but anywhoo. Another alien walking around disguiseless is not good for his own undercoverness, so he's going to subtly sneak away from the main crowds to confront this extremely-tall-purple-guy-who-is-not-Tallest-Purple.
He'll get his attention by yelling, because that's sneaky.]
Hey! Heyy! [Look, Goliath even gets a little arm flailing!] What do you think you're doing??