(Bloomberg) -- Welcome to the era of ETF mashups, whose issuers act like Dr. Frankenstein and combine popular strategies hoping the result will be greater than the sum of its parts.

Maybe such creativity is expected when there are more than 1,700 ETFs and basically everything under the sun has already been ETF-ized. The question is: Do mashups offer an exciting new investing opportunity or just create financial mush? Here is a look at a few of the more promising FrankenETFs:

Last month, PowerShares mashed together two popular strategies¬ócurrency hedging and low volatility¬ówith the PowerShares Europe Currency Hedged Low Volatility Portfolio (FXEU). FXEU tracks the 80 least-volatile stocks in the euro zone and uses derivatives to hedge out the currency.

The question here: Do investors need really need less volatility when hedging their currency exposure? Currency hedging already lowers volatility. The jury is still out on whether that is overkill, but since its launch, FXEU is up 2.7%, besting the $20 billion WisdomTree Europe Hedged Equity Fund (HEDJ), which is up 2 percent. Beyond the early outperformance, FXEU's true added value may be the low fee of 0.25%, making it by far the cheapest of any currency- hedged ETF. In contrast, HEDJ charges 0.58%.

Last week a suite of new ETFs were launched by Highland Capital Management that attempt to tie together the theme of tracking stocks held by hedge funds with actual hedge fund strategies used by funds in real life.

For example, the Highland HFR Equity Hedge ETF (HHDG) holds stocks that actual hedge funds own, just like the popular Global X Guru Index ETF (GURU). But, unlike GURU, it includes the short positions taken by hedge funds doing actual equity hedge investing. Highland calls its attempt to combine the best of both worlds "alternative beta."

BlackRock has also gotten into the mashup trend. It launched the iShares Commodities Select Strategies (COMT) late last year. Doesn't sound like a mashup from the name, but it is combining two entirely different asset classes: commodity futures and equities. Besides the commodity-producing stocks, it holds a wide spectrum of commodity futures, ranging from energy to livestock. This is a logical idea, considering many investors use both to play commodity prices and diversify their portfolios.

The mashing doesn't stop there as COMT is also actively managed. This is to help navigate around a dangerous and sometimes costly futures market. The fund is also structured in a way that gives it "normal" tax treatment similar to an equity. COMT has amassed $319 million in assets since its launch last October. Not bad, especially for anything with commodity in the name. 

Some other recent notable mashups include the Emerging Markets Internet & Ecommerce ETF (EMQQ), the PowerShares S&P 500 ex-Rate Sensitive Low Volatility Portfolio (XRLV), and the WisdomTree Markets ex-State-Owned Enterprises Fund (XSOE).

Look out for more of these mashup products. Just make sure you do your due diligence so you end up with a cronut and not cotton-candy fries.

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