Said gas giant is about 5 times the mass of Jupiter, hence a Super-Jupiter. This gas giant is rogue and has no parent star. Its composition is the same as regular gas giant, i.e. it is composed of hydrogen, helium etc. but here's a catch.
The gas giant, when it formed, accidentally swallowed up a neutron star, which is now located at the center of the planet. The neutron star in question is a pulsar with 1.8 solar masses with a rotational speed of over 60x a second. The star is embedded in the planet's rocky core. Surface temperature of neutron star is about 1,000,000 K. Sort of like a Thorne–Żytkow object
What would happen if a Gas Giant had a neutron star at its core?
I guess that the neutron star's gravity and extreme temperature would cause interesting phenomena such as wind patterns, and mascons happening at various places.
EDIT: This question does not ask what would have happened during the collision. Rather, this question asks what would happen to a gas giant with a neutron star at its core.