When did the twix bar become popular?
long time ago
No, A twix bar would be considered a heterogeneous mixture. The cookie and the caramel (not to mention the chocolate) can be physically separated from each other and they are not identical. By definition, a homogeneous mixture must be uniform (or identical) throughout the sample. Twix is not uniform.
The following flavor varieties either were or are still in production in various locations worldwide. Peanut Butter Twix Cookies-n-Creme Twix Chocolate Fudge Twix Triple chocolate Choc 'N' Orange Twix Twix Mint Mint Slice Twix Orange Twix White Chocolate Twix Dark Chocolate Twix Coffee Twix Twix Java Twix Cappuccino