Ways to surprise your sister on her birthday - or 'just because'! These surprise ideas make perfect birthday celebration ideas for your sister, lots of unique birthday gifts for your sister and birthday celebration ideas! How can I surprise my sister? Prank gifts are the answer! This is where you prank your sister, with a gift she's sure to love! You could wrap a funny item up to 'give' her as a present - for example, a spoon! - and watch her reaction before you gift her the real present, or…