Three episodes in, what are we getting from Lab Rats? For the majority of the episode, more of the same is the answer - and by this point in the series you've probably decided whether or not that's a good thing. But if you gave up after the first two episodes, then maybe - just maybe - you made the wrong decision.

But more of that later. For the third week in a row, Lab Rats starts off with an excellent idea for the main plot - or rather, for sparking off the main plot. Week one: cloning. Week two: cryogenics. And now, week three: protesters against animal testing. This is using the situation of the show to its fullest - not making it into a standard workplace sitcom but with mad things happening which just happens to be set in a laboratory, but intelligently using the concept as a means to spark off stories. Nice also, to see the concept used as a means of revealing the characters - Professor Mycroft is fascinated by the protesters as a breed, Brian just wants to do various unpleasant things to them (not for nothing do we see 'Brian's Tazer Mentions Jar'), Dr. Beenyman just wants the whole thing to be over, whilst Cara is happy because she gets to invent something again. Broad strokes to be sure, but it's all a good basis for the comedy - the show has got the fundamentals of the situation and the characters right.

Speaking of the situation, one interesting production point is that it's obvious by now that the show has no interest whatsoever in taking you out of the confines of the lab (apart from to the Dean's office). We don't even get scene-setting location shots. It's the very ultimate in the enclosed space that is the setup for so many successful sitcoms - and whilst the lack of extensive location shooting might possibly be a budget issue, the lack of a few establishing shots is unlikely to be - this is a specific production decision. I rather like the clarity this gives the show - after all, would establishing shots of the university actually add anything? - but it's very unusual. (It's interesting to note that Linehan slags off the establishing shots he uses in Series 1 of The IT Crowd in the commentary, and doesn't feel they worked - although it didn't stop him using them for Series 2! But I digress.)

The two main plotlines this week work incredibly well. On one hand, you've got the team trying out various security systems to keep the protesters out, and with the other, you've got Dr. Beenyman negotiating with various protesters, nicely set up with another of his excellent two-hander scenes with the Dean:

DEAN: If there is one thing I have learned in my many years in academic administration, it is that the best way of solving problems is by negotiating. People like to negotiate.
DR. BEENYMAN: No one likes to negotiate.
DEAN: Everybody likes to negotiate.
DR. BEENYMAN: There might be a few people who like to negotiate.
DEAN: Most people like to negotiate.
DR. BEENYMAN: Alright, some people like to negotiate.
DEAN: Done.

Unfortunately, every time Dr. Beenyman tries to negotiate with a protester, he ends up offending them - due to the various security systems. And whilst that sounds clunky on the page, it really, really works, due to some clever writing - both structurally, and for the material itself. The idea that Dr. Beenyman - his eyes damaged by an overly-powerful retinal scanner - would then get into trouble with a protester with a "chronic blink on him - he thought I was mocking him" is a nice idea. But the idea that "I was getting away with it at first because we were in sync - it was only when I sneezed and threw the timing out that he cottoned on..." is superb. Similarly, offending a protester who "had a little tic" because you're busy throwing your arms up in the air to disturb the motion sensor to stop the lights going off is great - but Minty's off-the-cuff remark that she missed the tic originally because "they were all doing a Mexican wave at the time - in fact, I think was him that set them all off..." just lifts it.

This is good, funny material. Even better from a structural point of view, these aren't two completely separate plotlines that only come together at the end - this is proper intermingling of the two strands. It is excellent sitcom plotting. And not only that, but you get the lovely idea of Joan Armatrading producing T-shirts with Dr. Beenyman's face with the word "WAZZOCK" underneath it.

Which perhaps makes it all the odder that the show is making mistakes in the setup of some of the jokes themselves. The most obvious example is with the new security system that Cara designs to keep out the protesters - the aforementioned retinal scanner. Which involves all the cast having to wear strap-on cardboard cutout eyes to their heads. (If you don't think that's funny, then by Episode 3 you've been sticking with the wrong show.) She demonstrates how they're visible in the dark by switching the lights off... and suddenly, we cut to two protesters - who we've never seen before, and never see again - who run in, are terrified by these weird glowing creatures the lab has obviously created, and run off shitting themselves.

It's a great idea for a joke (and there's a lovely moment prior to it where it cuts to a wide shot of the cast all wearing the strap-on eyes) - but the setup is all wrong. If the two protesters had been seen two minutes before - however briefly - then it would have been far funnier - the setup, and then the payoff. Here, they're doing the setup five seconds before the payoff, and it doesn't work. It just comes out of nowhere. Even worse, the fact that this is the first time we actually see any of the protesters - their presence being portrayed by crowd sound only up until this point - makes their appearance really jarring.

Indeed, a similar problem that affected the climax of A Snail. All the fundamentals have clearly been thought about, but sometimes the day-to-day setup of the elements themselves falters. Either the writers are just getting the structure of the show wrong at these points by mistake - hey, it is Addison and Cooper's first TV sitcom, to my knowledge - or it's a deliberate decision to try and surprise the audience by not giving them chance to predict the joke. If it's the latter, it's a nice try - but it's not really working. Setup and punchline is the entire structure of comedy - and besides, done right, the anticipation of a gag can make it funnier. Still, it's important to note that, whilst a recurring problem, the show does get the setup of other jokes absolutely spot-on - as we'll see.

Because the show is breezing along quite nicely - and then we get the final gag. Dr. Beenyman, who as we've mentioned, has been accidentally offending the protesters he's been trying to negotiate with all episode, puts a baked potato in the microwave, which explodes - leaving him in blackface. Just as Joan Armatrading - who's been protesting outside - comes in to have one last crack at sorting things out. And all of a sudden, the programme lifts from being a nice, likable sitcom, to being absolutely fucking hilarious. (And really, any of people on the net who think this joke is racist - just take a look at who the butt of the joke is here, rather than being reactionary.) This is the perfect running, escalating gag. Moreover, the makeup is perfect to sell the joke, and Addison puts in his best performance so far with it. And to cap it all off, the final "Oh, for f-" running gag works perfectly for the first time, simply because the joke has been set up properly throughout the episode, and the situation warrants that reaction. And finally, the series reaches the heights it's clearly striving for.

Even the actual microwave itself is set up in the first two minutes of the show!

And yet, the show still has problems. The show certainly manages to project that all-important likable atmosphere (and it's only mentioned so much because so many shows completely fail to do it these days) - but the laughs just aren't quite as big as they need to be. And let's be clear - they do need to be. This is a big, silly sitcom, which is trying to do no more than make you laugh, and make you laugh hard. That's no crime - in fact, it's hugely laudable - but if you're going to do that, you damn well need to make sure you deliver. When it does, as with the final joke in the show, it's magnificent - but the rest of it is not quite there yet.

This is down to a number of factors. There's still a few too many weak jokes here (was Cara's confusion between "ink vat" and "including VAT" really worth keeping?) The show is also missing more of the big moments that you need in this kind of sitcom - the kind of moments that this show ends with. But perhaps most importantly, despite the excellent structure of the main two plotlines, the show still isn't quite getting in the right rhythm for farce. That final joke is great, and it's all been set up properly - and yet note that I use the phrase "breezing along quite nicely" above. The show should not be breezing along quite nicely at that point - we should be headlong into the farce. It almost feels like everyone on the writing and the production don't quite realise that this is the show they should be making. If there's one bit of advice I could give for the next series - and for all the complaints, I really hope it gets one - it's: go for broke. Build the pace throughout the episode. Make a farce.

Still, for all the moaning - this is the best episode so far, if only because of that final joke than anything else. Lab Rats has cemented itself as a lovely way to spend half-an-hour on Thursday night. It's still not quite reaching the heights that it could do, or what the very best sitcoms manage, but there's nothing to hate about a show that delivers a nice, pleasant half-hour of comedy, and is something to look forward to all week. And that final joke really shows what the show is capable of.

And come on - who can't like a show that has a character named Minty Clapper?