I've always loved Coogan's ad lib "No manners, but what a critic" after the horse shits on the set in the background of KMKYWAP.
I don't know if it's exactly oft-forgotten but his new comedy character 'Camp David' is something I find impossible to watch just the once. "Wooooohhhhhhh, hello, Alan!" The fact it's obviously his voice.
As someone else has already nominated the enduring pathos of Joe Beazley and Cheeky Monkey is for me the high watermark of all Alan Partridge things. I found it both hysterical and faintly sad on its first broadcast in 1994 and I'm still a bit obsessed with it to this day, a plaintive still image of Joe Beazley has been my work screensaver for a long while now. John Thomson is just perfect. There are so many tiny details to savour in his brief performance.
His entrance when the puppet's limitations are immediately apparent and he has to pretend the monkey is intent on pulling him across the stage away from the mic. "What do you get if you cross Fred Flintstone....no, not what if you cross...." The bleak brilliance of Cheeky Monkey going bezerk with its head to the sky during the fluffed first "Yabba Dabba Dooooooo!" "The other week....pack it in, you!" "They've got the biggest rollercoaster in the world, it's massive...(flounders) Int'it? (makes monkey vigorously nod)" Probably the best bit, when Cheeky Monkey's hands become separated and he quietly mutters "Oh, god", then fails to reattach them and just stands there with one of the hands lamely pressed against his chest. The cutaway to a nervous looking Alan. "It's his fault, ladies and gentlemen, he's made me forget!" Fuck man, it's so brilliant and I might have to watch it again now.
"Hold onto your sides, they might just split!"