Everyone needs a mug with rocket engines. This is a push fit base for a mug that allows you to fit rocket engines.

I printed the base and the engines separately and then glued them together. The key is to carefully measure your mug to get the radius of the mug correct, this is so it can push fit on. The fit is snug and loosens a bit with a hot drink in owing to differential expansion, it may be worth printing small and fitting when hot.