What could happen if I miss a dose of clomiphene?

Likely nothing... Clomid (clomiphene) has a relatively long half-life, meaning its metabolites last a fairly long time in the blood to give the desired effect. If you miss a dose, it likely won't matter as long as most of the pills were taken as directed. Be sure to let your doc know, though. Good luck!
Nothing. Most likely there is no danger. Most doctors prescribe that for 5 days. You can always take the missed dose a day longer (so on the 6th day). But most likely there is no significant effect of missing one dose.