Bart nearly had the darned thing when Wally jerked it away again to-- well to be a jerk! This was the problem with not having hit his growth spurt yet; Wally could still hold things over his head and make him jump for them.
"Okayokayfinegimmegimmegimme!" Bart might have threatened to tell Iris that Wally was being mean to him, were this a typical family at least.
Fortunately for Wally, there was nothing typical about the West-Allen family tree.
Then again, from the looks they were getting in the grocery store, it seemed like everyone else realized that fact too...