When you see an old man riding his bike down the road slowly and it's your choice if he gets hit by some toast.
This is how you could use Geezer On A Bike in a conversation.
You: Hey Milly! How's it going?
Milly: Good! I was just about to eat some toast (optional)
You: Oh well... Look at this geezer on his bike *points at him*
Milly: I can imagine him getting hit by toast