Have you heard the joke about the gas lighter?

Comments:
I’m gonna tell everyone I made that up
oh this is so good and then I’m going to gaslight them into thinking I made it up
my brain totally erased the word "gas" from the sentence, it was just like "no, that's just a filler word, it's not important"
took me three reads to understand but thats on brand for my brain so its ok
I told you yesterday remember? Damn this is like always you never listen and you are so forgetful.
remember??? all your friends laughed and you didn’t get it
I don't get it, can someone explain?