Fancy a sleepover at the Harold Washington Library? Cartoons projected onto the John Marshall Law School building? A sunrise concert in Millennium Park? Ty Tabing, executive director of the Chicago Loop Alliance, used the first Friends of Downtown brown bag presentation of the year to get us all jazzed up about the first Looptopia, an all-night festival that runs from dusk on May 11 until dawn. More than 100,000 people are expected to attend the event, which will feature more than 75 performances in 30 different venues in the Loop. Similar overnight cultural and arts festivals have thrived in Paris, Rome, Brussels and Montreal, and the Loop Alliance is betting Looptopia will grow into an annual downtown event in Chicago.