What does “like an elephant's eye” mean?
This is an example of the use of a nonsence word.
"We seldom ever have an argument, but if it is, it's about something like an elephant's eye."
nonsense words TFD
words are used in literature for poetic or humorous effect. Proper names of real or fictional entities are sometimes nonsense words.
The sentence could have been written:
"We seldom ever have an argument, but if we do, it's about the weather on mars!"
meaning
"Our arguments were rare and were about nothing of significance."