There have been a few missteps along the way, but in general the last decade of Lego games made by Traveller's Tales have been fantastic. The innate qualities of Lego - its universally understood design, its magnetic tactility and its inspirational capacity to be anything you can imagine - have been hitched to the deep worlds of licensed properties like Star Wars, Harry Potter and The Lord of the Rings, and brought to life by the magical potential for games to let players build and destroy things in seconds, whatever the scale. It's become the formula where everyone wins.

Even so, Lego City Undercover - an open-world matinee crime romp following an undercover cop's adventures in the plastic metropolis - was a risk. The Lego City line of models may be among the Danish toy company's top performers, but while fire-trucks and police cars may appeal to a seven-year-old on spec, the rest of us take more convincing. Even the kids may balk; past Lego games have involved collecting thousands - millions - of coin-like studs which can be invested to unlock new characters for use in Free Play, but how can a security guard, a limo driver or an ambulance worker hope to capture anyone's imagination to the same extent as a Han Solo or Professor Snape? Wouldn't you go straight to the exit rather than pausing to collect anything?

Lego City Undercover answers this challenge in a sensible way: it distracts you from it for so long that it becomes irrelevant. You still collect studs - millions of them - and you still use them to unlock alter egos and vehicles that you can have heli-dropped at locations around Lego City, but now there's another currency that takes precedent. Super Bricks, left behind when you smash items of scenery, can be saved up and spent on 'Super Builds' - large structures like fairground rides, ramps and suspension bridges, which often have gameplay implications and are assembled in fast-motion as a swooning camera salivates all over them.

Super Bricks hold a greater attraction than studs - partly because Super Bricks are just cooler-looking pieces of Lego than studs, and partly because Super Builds like helipads and vehicle call-in points are so desirable - and they are woven expertly throughout the open-world city. Whenever you drive down a street you're constantly carving a path that takes you through every streetlamp, kiosk, cone and railing you can smash in order to collect some more, assisted by a multiplying effect that grows for as long as you can chain scenery hits together.

The game's Wii U exclusivity has brought a few Nintendo references with it, which are subtly integrated and worth watching out for. I haven't pictured any here - I wouldn't do that to you.

The lack of a licence hasn't stifled Traveller's Tales' script, either. (Actually, it's sister studio TT Fusion at the controls.) As undercover cop Chase McCain, hot on the heels of arch nemesis Rex Fury, you discover you're in a world of unlicensed references instead - like an ice-cream parlour pastiche of GoodFellas' single-shot nightclub scene, or a kung fu master inspired by Morpheus who is also a part-time plumber ("Empty your mind - as you would a radiator before replacing it"). When you rob a bank to impress a mob boss, the vault opens to the sound of Ode to Joy. Yippee ki-yay!

After a while, you realise it's not just the movie gags that hit home - it's everything. Each mission is soundtracked by jokes delivered through PA, video link or an on-screen companion, and as you walk or drive around Lego City you're bombarded with tickling radio messages or NPC dialogue. (I still get a kick out of the guy next to the door when I leave the police station who declares, "If I make two more arrests this month, I get a WAFFLE iron!") This is the same brilliant conveyor belt of winking tributes, dad jokes and slapstick gags that you expect from Traveller's Tales, and while licensed Lego games have always had that, Lego City Undercover makes it more obvious than ever that it's been down to the dev team rather than the licences.

The Nintendo Difference Lego City Undercover is a Wii U exclusive and therefore, as you might imagine, it makes extensive use of the system's unique GamePad controller. Most of the time the GamePad is used to show you a map of Lego City, but it's also called upon wherever you might need a touch-screen interface. The designers sometimes use it to a fault, in fact - video link-ups to other characters would have been better as window-in-window images on your TV screen so you could glance at them while you keep playing - but they also do some fun things with it, allowing hero Chase McCain to see through the environment and isolate collectables or eavesdrop on conversations. Nintendo fans hoping that Traveller's Tales would unlock the true potential of the GamePad will have to keep waiting for that, however, because if anything Lego City Undercover highlights one of the GamePad's shortcomings: the way developers keep using it as an in-game analogue for smartphones and tablets. Using maps, flicking through catalogues or using the GamePad to input data all invite too much comparison to equivalent experiences on iOS and Android devices, and that comparison is never going to flatter the GamePad, which feels awkward and dawdling next to those multi-core glass-faced smart-beasts. In truth, Lego City Undercover doesn't need to be on Wii U at all. Even the best GamePad features could be recreated on a single screen without too much difficulty. Who cares, though, when the game is this much fun?

Eventually, of course, there will be no getting away from the mild banality of unlocking a fisherman rather than an Aquaman, but there are so many hours of fun and laughter to get through first that I found it hard to be bothered. The game beneath these tantalising collectables, glinting jokes and warming cut-scenes is really substantial. It has a fairly standard spine: classic, fixed-perspective Lego story missions embellished with open-world car chases and rooftop free-runs, along with all sorts of side activities like point-to-point races. Those may not jump off the page, but they do quietly glue you to the screen.

Lego City itself feels quite passive to begin with as you tear between mission objectives - lacking the character of Liberty City's many different boroughs and neighbourhoods, or eye-catching landmarks like Crackdown's Agency Tower - but once you stop and zoom in on an area, you realise it's been dressed very cleverly. It doesn't matter if you're circling a log cabin in the countryside, poking through alleyways on an industrial estate or clambering over shipping containers at the docks; you quickly find little breadcrumb trails terminating in a hidden character, a Super Brick stash or a side mission, or little squirts of pointless fun like assembling five bubblegum machines or winning a basketball mini-game.

It's all anchored by another classic collectable, the Gold Brick, and there are 450 of them to find in Lego City Undercover. You get them for finishing missions and side activities, for unlocking disguise-swapping kiosks, and of course for completing Super Builds, giving you an even stronger compunction to go after the moreish Super Bricks. Gold Bricks have always had a similar hold over players to Mario's stars, so they're an apposite deterrent to boredom in a Nintendo console exclusive.

There are dozens of Super Build locations around Lego City - things like helipads - and although there's some repetition that doesn't stop you lusting after Super Bricks.

If you start probing for them in the first few hours then a row of doors covered in padlock icons becomes a common sight, because many abilities are tied into completing the story missions. But that's a path you'll want to tread quickly anyway, because the game is at its best when it sends you burrowing beneath its nondescript surface.

The developers certainly don't need Hogwarts or Minas Tirith to make this stuff interesting, because the rarefied design of the fixed-perspective story levels is just as clear in a trademark-free space centre or dinosaur museum as it ever has been in licensed surroundings. Every area is strewn with things to break, manipulate and collect, and the consequences of doing so are threaded so that you criss-cross areas between loot drops, surprise gags and puzzle gimmicks, topping up your enthusiasm at every step.

The story is pretty generic, but then it's mainly there to justify the jokes and tie things together, and on the plus side it's refreshing to play a game that is so artfully wholesome. Chase is constantly apologising for traffic violations and prangs (yelling out of the window that he'll be back later with his insurance details), there are no guns, and pretty much all the combat (of which there is only a token amount anyway) is based on self-defence rather than violent attacks - which must take restraint in a universe where people are supposed to be pulled apart at the waist and neck.

There are a few problems, but they are mostly limitations of the hardware. The draw distance and frame-rate aren't terribly solid, although this never interfered with my enjoyment of the game, and as with previous Lego titles the camera doesn't always lend itself well to precise platform jumps. With a heavy emphasis on the Wii U GamePad (see sidebar), the game also lacks any multiplayer features, which is unusual for a Lego title - it didn't bother me, but you should take it into account if that's a big part of your relationship with the series. Lego City Undercover is also guilty of some of the usual open-world genre sins, like long journeys between objectives and repetitive side missions. The biggest blemish, though, is the load times when moving between level interiors and the open world - these are weirdly long and the only time the game loses your attention, with not even a set of amusing tooltips to distract you.

The lack of words on the load screens is unusual, though, because in many senses this is a game - and a toy - completely defined by that kind of attention to detail. In the real world, Lego has fought off competition from rivals with its design quality - every Lego brick is stamped with an identifying number so the Danes can fix the mould that produced it, should anyone detect a defect - and Traveller's Tales has proven a worthy custodian of that heritage, something that Lego City Undercover happily extends.

It may not have a big-name sci-fi or fantasy licence to hang its hat on, then, but it turns out Traveller's Tales has itself been working undercover for a while on that front, lurking behind the smokescreens of Gotham City and the galaxy far away as it evolved into an accomplished developer capable of charming players with a mixture of great writing, twinkling level design and laudable values that keep you coming back regardless. Lego City Undercover isn't ceaselessly brilliant - open-world games seldom are - but it's a fantastic example of what makes Traveller's Tales and TT Fusion such special developers, and the worst I can say is that it's occasionally only fun. And you know what? I'll take that wherever I can find it.