Der Glückwunsch nur von zwei Leuten - Google translate gives me "The greeting of only two people" (when I don't use the whole phrase it also gives Glückwunsch as "congratulations" rather than "greeting," which is closer to what I think the comic intended). Is that pretty accurate, and would I be fairly safe in rendering it into English as something like "A congratulation between just two people" or "A congratulation between two people alone"?
Alles Gute zum Geburtstag - Google translate gives me "Happy birthday."
Also, for both of those, since I'm almost positive that the English translation given to me by Google is the meaning the person writing the comic intended--is the German actually correct for those phrases?
Thanks for your help!