It doesn't seem that the 'fake sign language guy' (Thamsanqa Jantjie) at Mandela's memorial service was a prankster, as some speculated
. Instead, it looks like he was a poorly qualified guy
who cracked under the pressure
and started signing nonsense.
Or perhaps he was communicating with extraterrestrials.
From the BBC
the man's signing seemed to have no grammatical base and kept repeating sign patterns when it was clear that the speaker was not using repetitive words. UK deaf news blog The Limping Chicken said the sign language interpreter had a "strange repetitive rhythm to his movements", and "the structure of his hand and body movements didn't seem to change no matter what the speaker was saying".