Mr. 20 is obsessed with the number 20. Reports about his age have been a little shady as he claims he has been 20 years old since he was born.
He lives on the 20th floor of Joe Evil Zincorporated, and is currently writing a 20 book series where each book has 20 chapters and all chapters have 20 pages. It's about a group of 20 people who go out on a series of 20 adventures to collect the 20 magical crystals that will grant them 20 seconds of unlimited power. Unfortunately none of his books have won awards yet but the 20th book (yes, he started with the last one) got 20th place in the Poolyt Surprise competition.
Mr. 20 only pays in $20 bills and buys things in twenties, but never gets anything on sale unless it's 20% off, and always leaves a 20% tip.
Joe lets Mr. 20 stay because he pays 20 times the normal rent (with a 20% bonus).