Both Uses

phenomenon
in
Great Expectations
(Edited)

If they had asked me any more questions, I should undoubtedly have betrayed myself, for I was even then on the point of mentioning that there was a balloon in the yard, and should have hazarded the statement but for my invention being divided between that phenomenon and a bear in the brewery.
p. 71.9 *

phenomenon = something seen that is of special interest
We were waiting, I supposed, for Mr. Pocket to come out to us; at any rate we waited there, and so I had an opportunity of observing the remarkable family phenomenon that whenever any of the children strayed near Mrs. Pocket in their play, they always tripped themselves up and tumbled over her,—always very much to her momentary astonishment, and their own more enduring lamentation.
p. 196.1

phenomenon = something that exists and is of special interest

Definitions:

(1) (phenomenon)
something that exists or happened -- especially something of special interest -- sometimes someone or something that is extraordinary

"Phenomenons" and "phenomena" are both appropriate plural forms of this noun. "Phenomena" is generally used in scientific or philosophical contexts.
(2) (meaning too rare to warrant focus)
In philosophy, a phenomenon is something as known through the senses. It is contrasted with a noumenon.