Spike perfectly describing Jareth and Sarah's relationship.
Spike: Right, so you're the masochistic immortal with a crush and she'd be the bossy bint with the power. Got it. Sod this. Been there, done that, bought the T-shirt, seen the re-runs. I'm out.
Jareth: ...Well, he had you down that.
Sarah: That was like seeing double.
Strip 145 My Eyes: Captain Hammer shows up and punches Erik for being an egghead professor in a mask (he also thinks Sarah and Christine are brainwashed). He then declares Erik's music sheets to be in code—they're in French, which he deems even worse. Sarah promptly pepper-sprays him.
And Jareth worriedly asks how long she's been carrying that.
Hammer's back in 174 Kablooie Part II where Bad Horse kills him with the Death Whinny.
Sarah: Wait, does the back of his shirt actually say "Support SOPA"?
Dr. Horrible: Of course. captain Hammer, corporate tool.
Strip 72 The Kid's All Right. Sarah's introducing her little brother Toby to everyone, and Aziraphale does one of his magic tricks, pulling out flowers.
Also, Aziraphaleslightly losing it over trying to figure out comic book continuity.
After it is resolved, Beowulf shows up about a dozen strips too late (he was "swimming in from GEATLAND! That takes time, OKAY?"). He also shows up buck naked. Thankfully Sarah is used enough to dealing with The Package to keep eye contact.
A meta-example, Word of Pika on why certain members of the cast (especially Erik) is allowed back at Sakura Sushi after the infamous Sushi Incident:
"The manager of the time of the Sushi Incident had a nervous breakdown and retired. New management and staff (including Cheryl) have been kept in the dark as to what exactly that Incident was, and while there have been far too many weird accidents around the Building and it is blacklisted for delivery (ROUS attacks, Bunny attacks, dirty old ladies, one Bogging, two accidental tripping of spikey deathtrappy contraptions, one report of a tentacle coming from the drainpipe, three cases of trigger-happy Elfshot, one encounter with Sweeney Todd in full "Epiphany" meltdown...)(and they compared notes with the local pizza chain), Cheryl has blackmail files on the restaurant's leetle failures to comply with regulations at times (legal student, remember) and will not hear of them banning her favourite eye-candy from actually coming to the restaurant."
Well the only thing we do know about that Noodle Incident is that it was caused by Erik and as James put it after the last extremely disastrous date "Eh. The restaurant is still standing this time...". (Given Erik's canonical tendency to endanger the local architecture when he's pissed off, it's not too hard to draw conclusions from there.)
The revelation of Jareth's chikkin phobia. It involves Erik squawking, Jareth screaming like a little girl and everyone else looking on as if to say "Did that really just happen?" Then Christine collects on a Side Bet with Javert.