The Origins (2) - S4.E21

In this, the first half-hour episode, a four-year-old Gumball becomes too much for young parents, Nicole and Richard, to handle, so they buy him a goldfish, but after the first six die from neglect, stupidity, and unfortunate incidents, Richard finds a special one in a shady red van who bonds with Gumball on a spiritual level. This gets put to the test when Darwin gets flushed down the toilet and must traverse a scary, new world to return home.