user2116: Writing my own blockchain parser, I have come across an unrecognized opcode in block number 142312. The relevant section of the transaction input is this:
"in":[
         {
             "prev_out":{
                 "hash": "0000000000000000000000000000000000000000000000000000000000000000",
                 "n": 4294967295
             },
             "coinbase": "fc70035c7a81bc6f4876c6036e4bc4080eaf81377bc9672828061491e79df5d4ddf1d65b058ccb30563f1f1c14f658607bd2c7138e87e480bcec3f5b91d041d041"
         }
     ],

fc corresponds to opcode 252, which is not listed in the Bitcoin wiki. How should I interpret this script value?
My block parsing program gives me the following raw coinbase script value:
fc70035c7a81bc6f4876c6036e4bc4080eaf81377bc9672828061491e79df5d4ddf1d65b058ccb30563f1f1c14f658607bd2c7138e87e480bcec3f5b91d041d041

That is, there isn't any opcode before the above hexadecimal string.

user403: It's possible for invalid scripts to exist in the chain. Scripts are only checked for validity when spent, and coinbase scriptsigs are never checked. You should just interpret coinbase scriptsigs as a chunk of arbitrary data that's usually (not always) a valid script. ScriptPubKeys can also be invalid: blockexplorer.com will print the script as "[error]" in such cases.

2116: <p>Writing my own blockchain parser, I have come across an unrecognized opcode in <a href="http://blockexplorer.com/block/000000000000046acff93b0e76cd10490551bf871ce9ac9fad62e67a07ff1d1e" rel="nofollow">block number 142312</a>. The <a href="http://blockexplorer.com/rawblock/000000000000046acff93b0e76cd10490551bf871ce9ac9fad62e67a07ff1d1e" rel="nofollow">relevant section of the transaction input</a> is this:</p>

<pre><code>"in":[
         {
             "prev_out":{
                 "hash": "0000000000000000000000000000000000000000000000000000000000000000",
                 "n": 4294967295
             },
             "coinbase": "fc70035c7a81bc6f4876c6036e4bc4080eaf81377bc9672828061491e79df5d4ddf1d65b058ccb30563f1f1c14f658607bd2c7138e87e480bcec3f5b91d041d041"
         }
     ],
</code></pre>

<p><code>fc</code> corresponds to opcode 252, which is <a href="https://en.bitcoin.it/wiki/Script" rel="nofollow">not listed in the Bitcoin wiki</a>. How should I interpret this script value?</p>

<p>My block parsing program gives me the following raw coinbase script value:</p>

<pre><code>fc70035c7a81bc6f4876c6036e4bc4080eaf81377bc9672828061491e79df5d4ddf1d65b058ccb30563f1f1c14f658607bd2c7138e87e480bcec3f5b91d041d041
</code></pre>

<p>That is, there isn't any opcode before the above hexadecimal string.</p>
 403: <p>It's possible for invalid scripts to exist in the chain. Scripts are only checked for validity when spent, and coinbase scriptsigs are never checked. You should just interpret coinbase scriptsigs as a chunk of arbitrary data that's <em>usually</em> (not always) a valid script. ScriptPubKeys can also be invalid: blockexplorer.com will print the script as "[error]" in such cases.</p>
