My kids were building a Mario house form an old wooden doll house. We had some leftover PVC pipe laying around, so I made a matching endpoint for it, glued it on the pipe, and my kids had some fun decorating it :-) 
This version was actually intended as a proof of concept, so it was a bit low res. But it looked nice enough that my kids decided to use it.

Made with Tinkercad. Feel free to copy and edit however you'd like:

https://www.tinkercad.com/things/l4z7akkb4jI-mario-pipe-end-for-pvc-pipe?sharecode=hsX6Vo0Lv1A87l7u5LjSqS0IbDYUXzDnVFAcssNi60Y