Into Yer Shtik

I don't think Mark considers himself "cooler" or somehow better than Kurt and Layne because he successfully quit smack and they didn't. There isn't really anything "cool" or superior about being a recovered addict, because that means you were an addict at some point. I think Mark is more disappointed and/or frustrated that they didn't make it. Yes, he can be an abrasive character with little tolerance for sugar-coating and bullshit, and that's bound to rub some people the wrong way. However, he's said himself that without his wife's ultimatum, he'd likely be a dead junkie too. "Cool" is probably about the last thing the members of Mudhoney would ever call themselves, as a group or individually.

The verse "made his myth, now he's trapped" refers directly to Layne's self-expressed contentment with becoming the junkie rockstar caricature he drew for himself on 'Dirt'. For as many times as he tried and failed to kick heroin for good, Layne eventually got to a point where he gave up and convinced himself that he was just meant to be an addict. It's very true that Mark considered this attitude pathetic, and a waste. You probably would too, if you have ever spent a significant amount of time watching an active alcoholic and/or addict slowly and deliberately kill themselves.

"Why don't you blow your brains out too?" along with that entire first verse, and the title of the song itself, are obvious jabs at all of the copycat 'post-grunge' bands like Candlebox, Bush, Seven Mary Three, Creed, etc. that ripped off the grunge sound for a quick profit.

The second verse is about Courtney Love and the Nirvana entourage.

I always thought "Susie" was Susan Silver, manager of Soundgarden and Alice in Chains and ex-wife of Chris Cornell. Honestly though, there were (and still are) loads of those self-aggrandized con artists running around collecting paychecks at the expense of the actual performers.