Hot rod bike

The piece for the contest will have many elements and tell a fun and relevant story of course. It will be humorous as well. Every funny story needs a punchline and this one will be told visually. The punchline won't make much sense until the rest of the story is told. Over the next weeks (maybe months) I'll be telling that story as I put together the pieces one by one. No point in tipping my hand to the other entries quite yet. Here's the punchline...