Fans of Twitter (NYSE: TWTR), social media stocks, initial public offerings and the exchange traded funds that hold social media shares and IPOs could be getting excited in anticipation of Twitter’s ETF debut.

After the close of U.S. markets Wednesday, Twitter will be added to the underlying indices of the Renaissance IPO ETF (NYSEArca: IPO), itself newly listed, and the Global X Social Media Index ETF (NasdaqGS: SOCL). [ETFs Confirm Addition of Twitter]

The issuers of both ETFs confirmed last week that will Twitter will be added to their funds after the close of U.S. markets today, or the end of Twitter’s fifth day as a public company.  SOCL also added Facebook (NasdaqGM: FB) five days after its May 2012 IPO. [Not Much of a Twitter Bounce for ETFs]

Global X did not confirm at what weight Twitter will enter SOCL, but it would not be surprising to see the stock immediately be a top-10 holding in the ETF. After all, the combine market value of SOCL top-10 holdings Pandora (NYSE: P), GRPN (NasdaqGM: GRPN), Yelp (NYSE: YELP) and Zynga (NasdaqGM: ZNGA) is less than Twitter’s current market value.

As for IPO, which has accumulated over $28.2 million in assets in just a month of trading, Twitter’s weight in that ETF was not confirmed, either. However, investors can get a sense for how big Twitter’s footprint in IPO will be by knowing the ETF’s methodology for new additions.

That is multiplying the 70 million shares offered by Twitter in its IPO by the stock’s closing price today. Rounding down to $42, that result is $2.94 billion, which would likely place Twitter somewhere among the top-20 of IPO’s current roster of 51 holdings.  Antero Resources  (NYSE: AR) is IPO’s No. 18 holding after raising $1.57 billion in its recent IPO.

Prior to Twitter, IPO’s most recent addition was real estate investment trust Brixmor Property Group (NYSE: BRX), said Renaissance Capital’s Kathleen Smith in an interview with ETF Trends. Smith also confirmed that Michael Kors (NYSE: KORS), currently IPO’s largest holding with a weight of almost 10.4%, will be depart the ETF when the fund rebalances next month. The ETF holds stocks for up to two years after their debuts as public firms. Michael Kors celebrates its second anniversary as a public firm in mid-December. [Post-Twitter What to Expect from ETFs]

IPO and SOCL have each traded slightly lower in the five days since the Twitter IPO.