emergencies are interesting. sometimes, depending on what runways we're landing on, we won't know that something us going on until 10 airplanes call us in the hold. a dead giveaway is when airplanes aren't released after 10 minutes or we get second calls asking for diversion instructions.
other times we just look out the window and see fire trucks rolling for something. the most recent one was a DL MD
-80 that suffered a compressor stall. before that, an AC
EMB-175 landed with it's nose gear actuator broken. that caused the gear to turn 90* and ended up in a pretty interesting landing. the crew did an amazing job, they kept the nose up for a good 2000 ft before dropping it and stopping in another 500.
all in a day's work though...