Happy, Sleepy, Sneezy, Bashful, Dopey, Doc, and Irate? Doesn’t work for me. 
“pissy” is closer to “grumpy” in my idiolect (though pissy has more of an edge to it). “Really really pissed right now” is closer to “irate”
grumpy
If you say Grumpy enough times it sounds like some sort of mild medical condition.
4 more yes… Clearly they want the spanking I offered.
OK, I don’t know what happened to what I typed but:
grumpy and irate are not close enough that I would call them synonyms.
I voted yes, without reading the thread, because I might say I was a bit grumpy about something that I was actually really angry about, to deliberately down-play it. But in the context of a high school reading text, no, they are not synonyms.
I voted No. An irate person is much more fun to watch than a grumpy person. 
(I imagine an irate person as someone waving his/her arms whilst screaming-yodelling.)
Not even close. If I’m irate, I’m enraged. Throwing things, yelling, I’m *shaking *I’m so mad.
Grumpy’s not even in the same ballpark. Hell, it’s watching an entirely different sport.
No, unless I’m going for understatement.
ETA: Did you know a vote counts as a post? I had to wait the 60 seconds here.
Absolutely not! There are huge shades of meaning between “grumpy” and “irate.” They’re not even close to being similar.
Grumpy refers to an overall mood of irritability.
“Irate” means something quite different altogether, a heightened state of rage, usually as an immediate reaction to something.
Grumpy is inward. Irate is outward.
Very true.
Forget semantics. Grumpy was a dwarf, and Irate was not. They are not interchangeable.