Attention holiday shoppers: If you look hard enough in your local bookstore you might find an amusing little book by Justin Heimberg called “Who Would Win? A Guide to Great Imaginary Showdowns.” A humorous tome pitting opponents both real and fictional against one another such as Dracula vs. Frankenstein's monster and apples vs. oranges, one of the book's more interesting what ifs questions the loyalty and fandom of Parrotheads vs. Deadheads. With all due respect to the deliciousness of a good margarita, it's difficult to ignore the impact that thousands of tie-dyed-T-shirt-wearing, concert-recording hippies have had on the longevity of the Grateful Dead. Leading the front lines of the hypothetical battle would, of course, be Dark Star Orchestra, one of the most respected and well-known Grateful Dead tribute bands around. With Donna Jean Godchaux and the Tricksters, it's scheduled to perform the National on Tuesday, Dec. 29, at 6 p.m. $25-$28.