The DNS server that tells you stuff you already know.
Notdns?
A silly play on words with two meanings: First of all it's not a DNS server, because it lacks virtually every feature a normal DNS server provides. Also, it works in emergency (=german "Not") cases, where you don't have the right DNS entries configured. Notdns works without configuration. In fact, you can't even configure it.
Howto and Features
Just run notdns.js, it will listen on the DNS port (UDP 53, needs special low port right under Linux etc.). You can then request DNS records which are generated on demand, based on your request. See these examples:
$ dig @localhost +noall +answer 127-0-0-1.a.some.domain
127-0-0-1.a.some.domain. 60 IN A 127.0.0.1
$ dig @localhost +noall +answer 12-34-56-78-987.srv.some.domain
12-34-56-78-987.srv.some.domain. 60 IN SRV 0 0 987 12.34.56.78.
$ dig @localhost +noall +answer www.google.de-80.srv.some.domain
www.google.de-80.srv.some.domain. 60 IN SRV 0 0 80 www.google.de.
Disclaimer
Notdns is obviously not complaint to any specification, buggy, insecure and useless. Have fun with it!