Attempting to $.extend Foundation.libs.tooltips,

callout.js

var callout = {
  create : 'overwritten object'
};

$.extend(true, callout, Foundation.libs.tooltips);
if (typeof callout.create == 'function') {
  alert('create() is still a function!');
}

if (typeof callout.create == 'string') {
  alert('create() is overwritten as a string!');
}