>>53100118Maybe a blend, it doesn't have to be a single influence.
Zenigata is the most expected inspiration given he's Japanese, and GF seniors grew during peak Lupin era. The official art does even the same pose. People have the idea that Japanese people only consume Japanese media, and Doctor Who was never a global phenomenon the likes of Star Wars or Marvel/DC, that's why everyone dismiss any Tenth Doctor influence.
But over the years Looker showed patterns that resemble the Doctor much more. Uses a codename, appears outta nowhere, temporarily partners with one single girl (Emma in XY, the nameless Beauty that found him in ORAS, Anabel in gen 7), refuses to use weapons, gets in cases that involve sci-fi and even time/space stuff. He looks goofy but is thoughtful and has a dramatic side, with hints of past companions that died on the lines -the Croagunk we saw in Platinum, the unnamed girl that succumbed to Guzzlord prior to partnering Anabel-.
His introduction is also timely, a couple of years after the Tenth Doctor. Early to mid 00s is also when James Turner starts working in GameFreak. If Looker is in fact partially influenced by Doctor Who, Turner could have had a hand on that.
Probably I'm wrong and it's all Zenigata, but there's definitely a case and it has more basis than just a seemingly generic detective-esque look.