~ちゃった ＝ ~しまった = ~しまう + past tense
Should be able to find it in your grammar book now...but if not, basically, it's like saying "I'm hungry" and "I got hungry already" or something like that? Sorry, seriously don't know how to explain it... ._."
ちゃう is a contraction of て+しまう. When attached to the Te form of a verb it it gives a sense of completeness and often has the connotation of regret, like if you were to say something that you regret, or were not suppose to tell a person. Or if you were to eat something that was for someone else.
If you have a grammar dictionary you would have to look it up under しまう. It can also be contracted as じゃった when attached to De (死んじゃった←"He's dead."(and he ain't comin' back))
In your examples, it's just there to express the extent of hunger/tiredness, perhaps without realizing it until then. You could translate it as, "I'm so hungry!" and "I'm totally exhausted." with or without exclamation marks!
Last edited by ComradeLewis; October 11, 2013 at 12:08 PM.
お腹すいちゃった ＝ お腹がすいてしまった
疲れちゃった ＝ 疲れてしまった
Also, ちゃった tends to also be used in cases where something beyond your control happens; 撃ちゃった would have a connotation of accidentally shooting, or of shooting without thinking and later regretting.