How Many Characters You Want(Self Explanatory): 1
What characters you want (4th years, werewolves, etc.): 3rd-6th year girl. Probably not a Slytherin(Unless you think she would have an interesting reaction; see below)
Level of RP (how long your RPs are, 1 line, 1 paragraph, 3 paragraphs, etc.): 1-2 paragraphs
What you want to RP about:
Basically Cid wants to experiment with a date for the Valentines Ball. This isn't an experiment in his own ability to find love, this is purely just out of curiosity. He wants to try and get a date and then do nice and gentlemanly things on the date to get the girl to fall for him. Then he's going to drop his 'nice' act, ditch her to see her reaction. Cid is able to do this not because he is a complete jerk, it is because he is borderline sociopathic(He usually doesn't feel things, i.e. guilt so he doesn't see this as a mean thing to do).
The alternative option would be to make this his history with a girl. it would have to be pretty recent as he is only a 5th year. Also, if this was something in the past I think it would have lasted for a few weeks or slightly longer, not just something that happened on one date. I think it would be pretty interesting to see how a girl would react.
Location (Hogsmeade, Hogwarts, etc.): Valentines Ball for first option, anywhere for second.