Metals decreasing in reactivity (Calcium, Magnesium, Zinc, Copper - Coats Make Zipping Conversations)
Rainbow colours (Red, Orange, Yellow, Green, Blue, Indigo, Violet - ROY G BIV)
Or things like
A for Artery, A for Away (Arteries carry blood AWAY from the heart)
V for Vein, V for Valve (Only Veins have valves)
Nothing happens, you just fail and move on.