Minecraftwiki says that if you do /give (username) 144, it should give you a mob head in its block form. However, when I try this, Minecraft crashes. This has happened three times. I don't know why it is happening.
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Based on a crash report provided in this issue, I believe with high certainty that this report may be a duplicate of MC-6744. If I am wrong, please go yell at Dinnerbone.
How am I supposed to yell at Dinnerbone?
Yeah, this is similar but not exactly the same. MC-6744 was for fire, this is for heads.

The other issue was first reported for just fire, because that's all they tested it with. After many duplicate reports and comments later, it was discovered to be lots of items that cause it. Heads are included.
Oh, ok. Sorry.