You give it multiple imdb title id's (eg: tt4154796) and it will look at the full cast and crew and find people who were in all of them

imdb_cast_overlap_finder.py

import re
import requests
from time import sleep


def unique(iter):
    result = []
    for x in iter:
        if x not in result:
            result.append(x)
    return result


class Movie(object):
    def __init__(self, id):
        self.id = id
        self.cast_url = f'https://www.imdb.com/title/{id}/fullcredits'
        self.cast_txt = requests.get(self.cast_url).text
        self.title = re.findall(r'>.+?</a>', re.findall(fr"<a href=\"/title/{id}/\"\sitemprop='url'>.+?</a>", self.cast_txt)[0])[0][1:-4]
        self.cast = unique([re.findall(r'/"\n>.+?\n</a>', x)[0][5:-5].lower() for x in re.findall(r'<a href="/name/.+?/"\s>.+?\s</a>', self.cast_txt)])
    def print_cast(self):
        print('   ', ', '.join([' '.join([x.capitalize() for x in y.split(' ')]) for y in self.cast]))

movies = []
num_of_movies = int(input('How many movies/episodes/shows do you want to check? '))
if num_of_movies < 2:
    raise ValueError('Number of movies must be at least 2')
for x in range(1, num_of_movies+1):
    movies.append(Movie(input(f'Please type in the IMDB title id for #{x}: ')))
    print(movies[-1].title, 'added.', end='   ')
    movies[-1].print_cast()
print('\n\n')

duplicates = []

for person in movies[0].cast:
    person_in_all = True
    for movie in movies[1:]:
        if person not in movie.cast:
            person_in_all = False
            break
    if person_in_all:
        duplicates.append(person)

duplicates = [' '.join([x.capitalize() for x in y.split(' ')]) for y in duplicates]
num_of_duplicates = len(duplicates)
print('\n\n')

if num_of_duplicates == 0:
    print('No duplicates found')
elif num_of_duplicates == 1:
    print('One duplicate found:')
    print(f'    {duplicates[0]}')
else:
    print(f'{num_of_duplicates} duplicates found:')
    sleep(3)
    for dupe in duplicates:
        print('   ', dupe)