Hey Stef, dear Moosers, there is a new implementation of lazy (or dynamic, as I call them now) inst vars for Moose. The new implementation is not based an wide classes, but on anonymous subclasses, and includes very strict sanity checks to guarantee type safety and Smalltalk's language model. You may only extend a base class with an inst var, iff name isString. name isSymbol not. name allSatisfy: #isLetter. (case allInstVarNames includes: name) not. class canUnderstand: name asSymbol. class canUnderstand: (name copyWith: $:) asSymbol. and you must implement the accessors in the class as follows class >> foo ^self dynamicInstVarNamed: 'foo' class >> foo: value self dynamicInstVarNamed: 'foo' put: value with this setup, we can guarantee that no tool is broken, neither the browser, nor inspector and debugger or senders- and implementors-of. Except for the first write access, access time on an dynamic instance variable is guaranteed to be the same as for "normal" instance variables. Please refer to DynamicInstVars and DynamicInstVarsTest on SCG Store, for a first draft implementation. cheers, AA