(Bloomberg) — Investors are rediscovering their appetite for the market’s speculative fringes.The shares of GameStop Corp. and AMC Entertainment Holdings Inc. — the poster-children of this year’s Reddit boom — are surging. Interest in special purpose acquisition companies has reignited with Chamath Palihapitiya’s blank-check firms leading the way. And Bitcoin and Ether are up after last week’s bonfire in cryptocurrencies.While the catalyst is unclear, retail traders appear to be driving the action. Touts are plastered all over social media with individual investors attempting to pump their bets on Twitter, Reddit’s WallStreetBets and chatrooms on Stocktwits.“The Reddit raiders are at it again,” Michael Pachter, an analyst at Wedbush Securities, said as shares of GameStop and AMC were among the most actively traded stocks Wednesday. “It looks retail driven to me.”Memes Are ForeverWhile the S&P 500 is virtually flat this month, shares of Reddit favorites GameStop and AMC are soaring. Including Wednesday’s gains, GameStop is up 40% in May while AMC has surged 95% over the same period.The pair of stocks have been among the best performers in a basket of 37 so-called meme stocks tracked by Bloomberg in the month of May. As a group, Wednesday’s 7.7% rally marked its best session since the retail mania gripped the market back in March.The gains are sure to bring more pain for short sellers betting against GameStop and AMC with the group down roughly $8.1 billion in mark-to-market losses this year, according to S3 Partners. With the retail investor movement regaining back momentum and both stocks having high short interest, there’s potential for a short squeeze, S3 Partners’ managing director of predictive analytics Ihor Dusaniwsky said by email.“Short sellers may start trimming their positions in the face of continued stock price strength,” he said. They had seen mark-to-market losses of about $475 million for the month of May alone prior to the latest spike, S3 Partners data show.SPACs BouncingThe speculative fervor may also be providing a boost for blank-check firms, which have accounted for nearly half of 2021’s record initial public offering volume.Virgin Galactic Holdings Inc., a space tourism business that merged with one of Palihapitiya’s SPACs, has surged 22% this month after a brutal decline earlier this year. Gains in the stock, popular with day traders, came after a successful test flight, and may be giving renewed life to the once red-hot SPAC market.Opendoor Technologies Inc., another SPAC associated with Palihapitiya, has jumped in recent days after falling to its lowest level since August. Meanwhile, two closely watched SPAC ETFs — the Defiance Next Gen SPAC Derived ETF (SPAK) and Morgan Creek-Exos SPAC Originated ETF (SPXZ) — are both up more than 10% from lows earlier this month.Crypto ComebackBitcoin and its crypto brethren have taken investors on a wild trip this month. As Bitcoin plunged as much as 54% from its February high, over 700,000 traders had their accounts liquidated in a 24 hour stretch, according to Bybt.com data.Investors, however, took the dousing in stride. Many fans of the notoriously volatile asset class used the dip as a buying opportunity.Bitcoin, the largest digital asset, is off its record high of near $65,000. But it’s managed to recoup gains from a recent low of around $30,000. On Wednesday, it hovered around the $40,000 level, meaning it’s advanced roughly 30% since that low a week ago. Meanwhile, the second-largest cryptocurrency Ether is up about 58% since its May low of $1,732.(Updates for S3 data in seventh paragraph.)More stories like this are available on bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2021 Bloomberg L.P.