There are three meaning or definitions for the word Yoyo. First there is the toy thought to have been invented in China, which was first mentioned in literature I believe in Greece in around 500BC. Next use is as an acronym created back in the early 70s meaning "Your On Your Own". I take credit for that one. The last is the one associated with the description of the toy in action and of Chuck and Sarah's relationship in Chucks mind, from what we see. One day he's up the next day he's down. Roller Coaster relationship also fits.

The only good thing to come out of "Chuck Vs the Beef Cake" is neither Chuck or Sarah died, and Chuck can't move in with Morgan. What a nightmare that would be for anyone. Besides what ever happened to Morgan and Anna being back together? Wouldn't Anna freak out for Morgan to get a place with anyone but her?