My son Norman likes to do tongue twister, saying certain sentences very quickly with their rather similar words. He collected some tongue twisters. He always persuades me to try memorizing tongue twisters. But I am not good at all. You may try these ones that he found in his favourite movies:
Rubber baby buggy bumper baby sitting service.
Betty bought a bit of butter but the butter is too bitter so Betty bought some better butter to make the bitter butter better