With Skittle bag, sometimes used to refer to miscellaneous heterogeneous mix of various narcotic pills, jumbled up in a bag (usually leftovers donated to the communal skittle bag). Often multicolored like a bag of skittles. Incredibly dangerous, as the actual contents are often unknown, and, thusly, the effects are often a surprise high.
Exo's also known as "tabs." These are pills that come in single-stack, double-stack, and triple-stack. They make you feel like your floating, or in a sense "rolling." They're notoriously taken in clubs to enhance the clubing atmosphere due to the lights and loud music.