Check this great plugin: Custom Wizard Plugin
I use it as a TOS legal pop up (by clicking accept, you agree to these terms…) and also to ask questions that I’ve hidden from the signup process (CSS to hide, then I ask them in the Wizard with more context). It works really well. The Wizard displays anytime someone signs up and I can then map fields to do anything I want (like send me a PM, update a Profile or do something funky with the API)