This thread feels like the twilight zone to me because I would do something like that, matter fact I have.
Basically to see where our chemistry is at and also to check her sense of humor.... nothing more attractive to me than a woman with a sense of humor.
I remember going out with this woman to eat (first date) , afterwards we went to Walmart because I had to grab a few items. I was squatted down like a baseball catcher looking at something on the bottom row and she playfully jumped on my back outta nowhere and I actually ended up on the floor on my butt.
I didn't get mad...in fact it showed me that she had a cool sense of humor and the way I reacted (I laughed) showed her that I have a playful personality myself.
We clicked and we ended up seeing each other for awhile.
I'm not sure about the REASON you did what you did but generally speaking, I personally don't see anything wrong with playfully tickling a first date or something along those lines. (Reading the room and "vibe" is important before doing it tho)
If she laughs then you may have a keeper. If she gets mad at you, it may be a sign that y'all wouldn't click anyways. (Not saying she's a bad person by the way, but everyone is different)