The Crazy Gang was a collection of zany comedians: three double acts - Jimmy Nervo and Teddy Knox, Bud Flanagan and Chesney Allen, and Charlie Naughton and Jimmy Gold - and, perhaps the most comical of them all, 'Monsewer' Eddie Gray, a slapstick maestro and comedy juggler of the first order. The acts had enjoyed individual successes but together they were a comedy phenomenon, packing theatres and appearing in a number of films, starting in 1938 with Okay For Sound (director Marcel Varney). 'Crazy' was the right word for them: their antics combined verbal gymnastics with farce and elaborate physical comedy, and it all seemed totally unstructured - lunatic stream-of-consciousness complemented by custard pies. Off stage too they developed an infamous reputation as practical jokers, and played many pranks on one another and fellow guest stars; hoaxes that ranged from the harmless to the cruel and, on some occasions, the downright dangerous. The team remained hugely popular for many years, Flanagan in particular being adored by the British public.
They are sometimes compared to the Marx Brothers - and that may have been true about the live shows that the Marxes used to prepare material for filming. I would think the parallel is closer to Hellzapoppin'.