(( In my AU, he is the oldest brother of the three skelebros, with sans being the youngest.
He was the royal sceintist, and studied both saving/reloading and was responsible for the “Fun/fun” units of measurements, and also the understanding of souls.
I ship him with Alphys for a p good reason. In Mettaton’s quiz, if you select “don’t know” for who Alphys has a crush on, it’s actually the correct answer. Mettaton then goes on to explain how Alphys has been studying into some hypothetical man who exists in an alternate timeline that would love her. Alphys then talks about how she did the studies, and it checked out. Mettaton, probably coincidentally, asks this being for a “SIGN”. That just screamed Gaster to me. I don’t like Undyne as a character and if I could I’d totally have my Gaster go into a relationship with an Alphys.
My Gaster does not speak in sign language, nor does he even normally speak in Wingdings. It’s simply what he uses to hide his notes from certain evil entities.
He was killed by Sans. This will be expanded on when my Sans and Alphys finish their blogs.
He was completely forgotten by everyone except Sans.
His favorite color is purple, he loves junk food and soda, and he is very well rounded in human society.