Board Thread:Fun and Games/@comment-27524978-20160317154321/@comment-27620479-20160416190941

Fanon Frisk and Sans: Someone shot them with a shrink ray or something, despite the fact that they are literal evasion pros. Seriously, Frisk reaches between waist and shoulder length compared to Sans, and knee to waist compared to Papyrus. Sans reaches about waist to elbow length compared to Papyrus, who seems to be of his normal height compared to Undyne and most depicted objects.

Canon Frisk and Sans: Have roughly the same height (of Papyrus' shoulders). Frisk is probably a bit shorter.