The concept of the Earth attracting another moon, even for a short time, makes me reflect on the moon we have.  

Why do we have only one moon?  Many of the planets have more than one.  Why one at all?  Mercury and Venus have no moons.  

Why such a big moon?  It's larger than the planet, Pluto.  It's two/thirds the size of the largest moon in the solar system, Saturn's Titan.  Yet Saturn is ten times the size of the Earth.  The ratio of our moon's size to planet size is only beat by Pluto and Charon which have a 1 to 2 ratio.  Titan is only 8% of Saturn's size, whereas our moon is 27% of our size. 

Why does our moon appear to be the same size as the sun?  In a total eclipse the moon and the sun match almost exactly. 

How did we get our moon?  NASA's website says "The leading theory is that a Mars-sized body once hit Earth and the resulting debris (from both Earth and the impacting body) accumulated to form the Moon."  But that doesn't explain where the "mars-sized" object came from or how a stable orbit was achieved. 

Why does the moon have phases?  Why do we always see the same side of the moon?  Why does the moon rise one hour later every night?

Some of these questions may seem silly and childish, but in science all questions are valuable.  It's sometimes the silly questions that lead to the most amazing answers.