WARNING: This article contains information regarding unaired/recently released episode(s) and/or project(s). It may contain SPOILERS.
The Prom King and Queen will be Finn and Quinn, but she will give the Crown to Rachel.
Apparently Brittany tells Blaine to wash the gel out when he first shows up at prom with it slicked down. It sounds like she had told him not to turn up in gel beforehand and he did anyway, so she tells him to wash it out, he does and he spends the rest of prom with his hair curly.