It's very unusual, but I guess not unthinkable.
And why would anyone make a 'speech' at church? You might be asked to do a reading from scripture or a poem, but not create a speech, that is what the priest does in his sermon.
Nonetheless, aside from thinking your mate is pulling your leg, you might be called upon to make a speech, even if it is at the party after.
Something along the lines of being a good friend of the mum and dad, how long you have known them, how you were delighted to hear they were having a child and how proud you are to be the godfather, but cannot understand why they named it Lucifer/Damian (I am joking of course). Nothing tooo sentimental, but you could also thank everyone for joining them on their special day and wish the child and it's parents a very happy and healthy future and assure them that you will be there to help them all the way.