https://github.com/blechschmidt/fakeroute
https://github.com/antifork/hopfake
https://github.com/jprenken/rickroute
https://github.com/sams-gleb/ipv4-traceroute-fake
https://github.com/job/ipv6-traceroute-faker
And so on…
I remember being a 13yo kid sitting on IRC doing exactly this for fun years ago back when IP addresses were cheap and easy to come by. But spoofing military IPs in the traceroute was more fun.