Like Heather, I must admit to loving "christ on a bike" without full knowledge of what it actually means. (It just sounds cool, and usually that's enough for me.) In my search for the truth, I came upon a few different theories:

1. Here, Christ on a Bike appears to be the name of an actual TV sitcom. Of course, it's British. Of course, the picture alone is enough to convince me to convert. To Britishism, I mean.
2. Another entertainment outlet seems to take the saying a little more seriously, combining the "bike" motif with a religion theme to create an "action sports/christian message movie." Wait, is this a joke?
3. On August 29, 2001, this kind blogger used "Jesus H. Christ on a bike" as an expression of distress. He stopped blogging just more than one month later. Coincidence?
4. Ah ha! Maybe it originated from "Kids in the Hall." This revealing post seems to imply so.

Okay, I'm not sure I've made any progress here. But I am certainly learning a lot of British these days. Plus, I like research projects.