Can big miniatures share their square in Arcadia Quest?
In the rulesbook on page 15 (Full or blocked spaces) it's said:


  Each Space can contain a maximum of two Characters at a time. A Space with up to one character in it is still considered to be free, since other characters, enemy or allied, can still enter it and shoot through it normally.


There's no mention of monster size here. Moreover in the same chapter, the example pictures a space with a lone troll (which is a big miniature) in it as free.