Have done it twice and am doing it again in October:

First time was Dad's 50th birthday, I was at uni and I turned up at the restaurant where we were having a meal with a close family friend. Everything had been pre planned, Dad was told I was away somewhere else to the extent that I phoned my parents from friends house and was talking to dad, kettle boiled and I said it was the kettle as someone was making me a coffee, friend was asking if i wanted milk & sugar by pointing. Dad was so surprised when i turned up, first thing he says was that I was meant to be at the place he'd been told I was and I told him no that'd been the previous week.

Following time took a bit more planning as 3 people got surprised, it was Mother's Day weekend 2007. My husband and I went over for it, dad had to tell Mum that my husband & I needed money to fix the cooker to explain the money being sent over to us, then he had to say he was giving my sister's then boyfriend now husband help with a job to explain going to pick us up. First to be surprised was my sister when we got back to hers, then dad took us to theirs and we surprised Mum, she did get emotional. The next day Mum took us down to Nan's house and we surprised her. Nan passed away 4 years ago today but this is one of my happiest memories of her.

October we're going over for the weekend before Dad's 65th birthday and he doesn't have a clue.