The writers of this show are absolute geniuses. They make a cartoon which is very often hilarious and sometimes moving and powerful. This particular episode is a great example of their talent.
Leela and the crew are sent to collect honey from giant bees- which is how the previous Planet Express crew died. Eventually, Fry and Leela get stung by one of the bees. Leela gets a small scratch but Fry got the full impact and she feels extremely guilty and depressed for causing his death.
What then follows is a series of bizarre hallucinations (including a hilarious scene where they all suddenly burst into song) and dreams and she becomes more and more certain that Fry is still alive.
This is an incredibly clever episode, with a great twist in the end and truly touching ending. I won't give away anything- but if you haven't yet seen this one, do so! It is the best work the crew of Futurama have done to date.