I always thought Wallace was a self-portrait of Nick Park. If your find a video interview with him, the way his mouth moves when he speaks is totally Wallace. It's uncanny.
https://www.ft.com/content/10922a92-00f2-11e8-9650-9c0ad2d7c...
> His mother was a dressmaker (“She still is really. She’s a spry 88”) and his father was a photographer. He was also — didn’t I read somewhere? — an amateur inventor. “ ‘Inventor’ might be too strong a word,” Park says. “He was always in the shed. ‘Oh, I’ll make a shelf’. ‘Oh, I need a stool, I’ll go and make one.’ ”
> Park’s father sounds like the inspiration for his own most famous inventor character. Yet the director didn’t realise the dad-and-Wallace connection until after making his first film featuring the suburban boffin and weird dog. That was A Grand Day Out (1989), his graduate movie project for the National Film and Television School.
> “He loved being compared to Wallace. I hadn’t realised the similarity till that film. It was after Wallace had built the rocket to the Moon in his living room that I thought, ‘I’ve made a film about my dad!’ ”
I can believe Wallace's gestures (and mouth movements) are Park himself, as that's likely the only reference material he had to hand.