This urge, every boss in the world has to be the funny guy in the house is completely inexplicable. However, it is there, and it is there to stay for a really long time. The sad part is that they are almost never funny. And when they are funny, it is mostly by accident (if they go all clumsy suddenly).
At times, you don't want to giggle or chuckle or even give a tight smile. So what is it then you can do? Because let's all be honest here, if you do not laugh at their bad jokes, they can get really angry. Seeing that you love your job very much, I have a few ideas in mind you can try out when a fake laugh isn't coming to you, no matter how hard you try.
There is a very slim chance of this excuse to actually work but hey you can try.
It might be dust or they might be going blind by seeing the worst joke execution ever.
*After 5 mins*
I am fine now.