Sans is a skeleton with sharp teeth, with one being gold. Sans' red eye shows to reflect how “corrupt” (mainly emotionally hopeless) he’s gotten, so when it flickers, it would be yellow and orange. Sans holds in a lot of emotional stress, so he’s constantly radiating his powers and eye 24/7, which mostly affects his jacket fur. and he has a very irritated and angry personality and can get frustrated quite quickly when provoked. Sans is a very flustered tsundere when teased.