The surprise when you look in the mirror after the act of going down on a woman in the dark whilst she is unaware she is menstruating.
Dude, what happened to your face?". "Strawberry surprise man........
The act of secretly filling your anus with chocolate syrup and plugging your butt with a strawberry. When this is done, the surpriser tells their partner that they have a surprise for them. The surpriser then proceeds to excrete the chocolate and strawberry into their lovers mouth.
"I gave my girl a strawberry surprise last night. Bitch loved it."