Probably not enough neutrons for them to be funny?The engineers at Boeing never got my jokes either.
A 3 neutron for of hydrogen has been made in particle accelerators and it has an extremely short half life.
4H (atomic mass is 4.02643(11) u) contains one proton and three neutrons in its nucleus. It is a highly unstable isotope of hydrogen. It has been synthesised in the laboratory by bombarding tritium with fast-moving deuterium nuclei.[9] In this experiment, the tritium nucleus captured a neutron from the fast-moving deuterium nucleus. The presence of the hydrogen-4 was deduced by detecting the emitted protons. It decays through neutron emission into hydrogen-3 (tritium) with a half-life of about 139 ± 10 yoctoseconds, or (1.39 ± 0.10 × 10−22 seconds).[10]