In the Mongo shell, if you type v=function(){}; <Enter> v. <Tab> and then hit <Tab> repeatedly, you cycle through completions of apply(, call(, constructor, hasOwnProperty(, propertyIsEnumerable(, prototype, prototype, prototype, toLocaleString(, toString( and valueOf(. I tried arrays, objects, Dates, ISODates and NumberLongs and didn't see any others with any repetitions. From reading the code, I see that this set of completions is coming from a JavaScript routine shellAutocomplete() in shell/utils.js, and this code sets a JavaScript variable _autocomplete. So, the bug seems to be in shellAutocomplete() or one of its helper routines:

> _autocomplete_
[
"v.apply(",
"v.call(",
"v.constructor",
"v.hasOwnProperty(",
"v.propertyIsEnumerable(",
"v.prototype",
"v.prototype",
"v.prototype",
"v.toLocaleString(",
"v.toString(",
"v.valueOf("
]
>