Fun house mirrors are a great tradition for Halloween because they are so flexible. You can use them in a genuinely scary haunted house to add a feeling of disorientation. Or, you can use them in a lighter, kid-friendly Halloween party to confuse and baffle the little ones. The easiest way to make one of your own is to simply bend a sheet of reflective Mylar. It is good enough for a Halloween party, and inexpensive enough for the lowest budget haunted houses.
Find an old, full-body mirror frame. Try to find a really big one, if possible. The taller it is, the more imposing of an impression it will make. If there is still a mirror in it, remove it.
Get a roll of mirrored Mylar which is slightly narrower than the frame. It just has to be narrow enough to fit easily through the frame, so about half an inch narrower is ideal. You can purchase mirrored Mylar at the link below.
Cut a sheet of Mylar that is just an inch or two longer than the mirror frame. The extra length will make the mirror curve when you attach it, giving a fun house effect.
Use double sided tape to attach the Mylar to the frame. Attach it to the top and bottom of the frame, leaving the middle free. Your mirror should bulge either forward or backwards in the middle.
Decide if you want to make a concave or a convex mirror. A concave mirror curves inward, while a convex mirror curves outward. Concave mirrors will make you look short, whereas convex ones make you look tall.
If you want a concave mirror, push the middle part of the mylar back slightly to give the whole mirror the proper bend. If you want a convex mirror, push the middle forward. It will stay in the position you leave it in until somebody touches it.
There are many different illusions you can get by bending your mirror in different ways. Experiment and see what effects you can get. You can sometimes find partial rolls of Mylar in artist recycling stores for very cheap. If your Mylar sheet is too wide, you can easily cut it with scissors.
Be careful when you mount the fun house mirror. If it is a concave mirror, the wall can push against it and flatten it, ruining the illusion.