The trick here relies mostly on comments that are valid for one language, but not the other (abusing Java's Unicode preprocessing). There are language pairs that offer no provision at all for embedding parts of code that another language won't see or misinterpret. E.g., I haven't been able to write a batch file that also works as a PowerShell script yet, although you can write a batch file that doubles as a VB script through clever use of a conditional jump.

No, but another one you can do it in is PHP and JavaScript

    function isEven($number) {
        return $number % 2 == 0;
    }

That's actually valid PHP code and JavaScript. But I think you'll need to use eval on that in the PHP vm because it won't have the `<?php`