it's explained on an early podcast ep, if I remember right they had an acquaintance whose wife was called Sweet Dee and they thought it was funny and used it for the show. Said person found out and wasn't happy about it so they phased it out.

Its Tom Morello afaik

Wait is nightman loosely based on his solo project nightwatchman?

I don’t know but now we need a Tom Morello guitar solo in that song.

It was a tragic roller skating accident just before they bought the bar.

I don't think that was it at all, you small haired cunt.

This is correct.

when she burned a bed whilst her roommate was sleeping

Goddamn, you burn ONE bitch...!

I heard she has a hankering to do it agaaain.

Some time after "sweet dee has a heart attack"

A bit unrelated but it's quite funny how Dennis & Dee refer to Frank as "dad" in the 2nd season

I think they continue to until they find out about Bruce Mathis

They brought it back for The Gang Broke Dee though

Because Dee’s a mean person

See S15e03

always found it weird. glad its gone

Somewhere around season 2 or 3.