Larry David's version of the Contract of Mutuum

The Contracts Re (= executed by delivery of a thing or 'res'), or 'real contracts,' constitute a category of nominate Roman contracts, among the oldest, gratuitous in nature (no interest is supposed to be charged).  One of these was the contract of Mutuum (a Latin portmanteau of Meum et Tuum = 'Mine and Thine'), the simple loan for consumption of fungibles.  The obligation is created when the owner transfers ownership to another party for consumption (money, grain, wine, etc.) on the understanding that the obligor will return - not the same borrowed thing (because it will be consumed) - but an equivalent value to the original lender.  It is stricti iuris, meaning that judges have little leeway in finding equitable exceptions to performance of these strict obligations.  They must be enforced, whether the judge or litigants liked it or not.  

Larry David and Jason Alexander illustrate for us with pens how real contracts might work and cause trouble in a modern context:

Here is the discussion of Mutuum contracts in Vinnius on Justinian: