It's Bubblefest on Sesame Street! Alan and Chris are in charge, and they've created some fun bubble challenges, including a competition to find the perfect bubble mixture and a pop quiz. But it's Abby and Elmo who blow everyone away with one really big bubble! George Lopez visits the Street to explain what liquid is. It's letter B day at Abby's Flying Fairy School, and Super Grover 2.0 uses his powers of observation. Finally, Murray experiments with bubbles, and things are very fishy in Elmo's World.