The phrase "catch some z" refers to sleeping or getting some rest. Some antonyms for this phrase could be "remain awake," "stay up," "pull an all-nighter," or "not get any shut-eye." Other antonyms include "rise and shine," "start the day," or "get going." Essentially, any phrase that implies being awake and active would be an antonym for "catch some z." It's important to balance rest with activity in order to maintain a healthy and active lifestyle, so while getting enough rest is important, it's equally important to remain active and engaged in the world around us.