You will hear 'asked' pronounced with a different vowel sound by native speakers from different parts of the world, but never with the /id/ ending. I think you have either misheard or the person you have heard saying this was not a native English speaker. The latter is the likelier option.

I agree with Jmat. Are you sure that the "ask-ed" pronunciation was from a native speaker? I've only heard it from learners.

No, this is not an exception. 'Asked' is always pronounced with a /t/ sound at the end. No native speaker would ever pronounce 'asked' as 'askid' in modern English.

Either you misheard, or the person was not a native speaker. Many people whose first language is not English have trouble pronouncing consonant clusters such as /skt/. So even otherwise proficient non-native speakers, such as Spanish-speakers living in the USA, for example, often mispronounce this word and say it as if it were two syllables.

The only verbs where 'ed' is pronounced as /id/ by native speakers are those with base forms ending in the letters 't' or 'd', for example 'wanted' and 'needed'.

The general rule is that if the final consonant is voiced, 'd' should be voiced too. If the final consonant is unvoiced, 'd' should be unvoiced (ie. it becomes a 't'). If the final consonant is already a 't' or a 'd', you have to add a vowel before the 'd' indicating the past tense so you can hear the sound e.g. you have to add a vowel between the two ds in 'waded', otherwise it'd sound exactly like 'wade'.

I don't think I've ever heard the 'ed' in 'asked' pronounced with an /id/ sound. Are you sure you heard that from a native speaker? It's possible it's just a regional variation I'm not familar with. I know in the southern US they often pronounce 'asked' like 'axed' (the 'ed' is still pronounced as /t/; the difference is that the 's' isn't pronounced before the 'k' and the 'a' is changed to an /æ:/ sound).

I see what you're getting about the adjective idea. There are certain adjectives that have final syllables pronounced as 'id'. These are the usual ones:

Naked

Learned

Rugged

Dogged

Wicked

Wretched

Blessed (sometimes)

Crooked

Beloved (sometimes)

Accursed

Legged (as in three-legged)

The only problem with your theory is that, unlike the words in the list above, 'asked' <em>isn't </em>an adjective. It's a verb in the past tense, and as such it is always pronounced as one syllable with a /t/ at the end.

If you really did hear 'askid', then it's almost certain the speaker was a non-native.