A prank is only harmless if the other person agrees it was.

Who decides whether something was funny is the person it happened to, not the person who planned it. Intent gets a lot of weight from the inside and almost none from the outside, because the only visible facts are what was done and how it landed. A joke that needs explaining was probably not one.

Ask yourself beforehand whether they would laugh if they could see it coming, and if you are unsure, assume no. When something lands badly, drop the defence of having meant well and apologise for the thing itself. Do not ask them to find it funny as a favour to you.