The Flash: 24 WTF Moments
20. Barry Ends Up In An Alternate Timeline
Despite Bruce Wayne (the Affleck one) warning him not to use his time-travelling abilities to try and save his murdered mother, Barry simply can't resist.
Given that his mother was stabbed to death by a home intruder when his father, Henry (Ron Livingston), went to the store to pick up a can of tomatoes she forgot to buy, Barry decides to rectify this by simply placing the can of tomatoes in his mother's shopping cart at the store.
But because tinkering with time and the universe has consequences, Barry ends up spat back out into an alternate timeline years before his own present, where this universe's version of Barry is still a powerless teenager.