Name: Gaster
Nickname: S.G
Age: is aged between Swap and Stars
Personality: gets flustered easily, calm and collected but he gets angry quite easily if you keep annoying him, enjoys a good pun from time to time, helps out around the house with what he can, on accasion he will spout Japanese curse words (that probably just confuses them), when angered run...,when bored he observers everything around him, don't give him anything with alcohol(an emotional/aggressive drunk), he is an insomniac meaning he hardly sleeps at all sugar only makes him more tired while giving him fruit  (like cherries, strawberries, dragon fruit, about raspberries) will wake him up, quietly hums to himself when alone (he is shy), he secretly loves flowers (especially cherry blossoms)
BrownENH hopefully this will be enough info for you... if you need more let me know! ;) and it's also up to you if you want to use him in your book but I'm letting you know that you can use him!
Enjoy!