Fancy meeting you here.

It's fancy meeting you here.

It's fancy meeting you here.在这见到你太意外了!
省略主谓,meeting you here做补语 .

这是祈使句，省略主语

fancy：谓语
you：宾语
here：补语

省略主谓语it is fancy,
meeting you here补语
没有宾语，系表结构