Just like in English, this section of grammar in German has hardly experienced any substantial additions or expansion for a long time now as the principle to have brought about these irregular verbs was actively applied for creating new words in the very early days of the Germanic languages. There is the, somewhat funny, Gesellschaft zur Stärkung der Verben (Society for the Irregularisation of Verbs) trying to account for the lack of development here (as was already mentioned in the question's comments).

Similarly to *sneak/sneaked* vs. *sneak/snuck*, the only comparative German counterpart I can think of right now is ***winken/winkte/gewinkt*** vs. ***winken/(wunk)/gewunken*** (to be waving one's hands) which, if not already, is most likely to enter eventually into generally accepted usage therefore coexistence with its older version.

Apart from this more or less unique new creation and addition, at times you could hear mix-ups of largely homophonic verbs because of lacking knowledge or consciousness about possible differences:

- ***hängen/hing/gehangen*** vs. ***hängen/hängte/gehängt***: Former is the intransitive version of *hängen*, the latter is the transitive one. So, they differ in that you would either *have something/be hanging* (*hing*) or *make something hanging* (*hängte*).
- ***leiden/litt/gelitten*** vs. ***leiten/leitete/geleitet***: Ever so often, mathematicians are not aware of how their (linguistic) *derivations* might not be as logically produced as they think. I would say this is just a spleen with various individuals coming from mathematical professions because they likeliest have never considered the possibility of a lapse of memory here.
- ***genießen/genoss/genossen*** vs. ***niesen/nieste/geniest***: By the spur of the moment, at times people say (jokingly) someone/themselves might *have enjoyed* to *have sneezed*.
- ***schleifen/schliff/geschliffen*** vs. ***schleifen/schleifte/geschleift***: For completion's purposes of this section, this pair, as a potential cause for having them mixed up, wouldn't really be that providing with a contemporary case of an occasion. They mean *to hone* (e.g. a piece of metal) vs. *to demolish* (a large structure, e.g. a castle)

It is also quite often the case that the past participle in German would be produced erroneously, but at the same time also that not as the main point to look at is the actual intention to become fulfilled or achieved through using one version or the other, i.e. by state or progression of the action implied by the verb.

Although being lexicalised with only one, many regular verbs are occasionally produced with two different past participles in German. For example, ***abgeschaltet*** vs. ***abgeschalten*** (to switch off [e.g. the television]) from regular root verb *schalten* which conjugated with either of the two auxiliar verbs in German (*sein*/*haben*) should be phrased accordingly in the German verbal tense of Perfekt as *[Der Fernseher] ist abgeschaltet* or *[Der Fernseher] hat abgeschaltet* (as above), but not as *[Der Fernseher] ist abgeschalten* or *[Der Fernseher] hat abgeschalten*.

This tendency to also use, like it would be here then, *[Der Fernseher] ist abgeschalten* stems in all likelihood from the non-obvious difference in usage of the auxiliar verbs with irregular verbs. (*ist gesprungen* / *hat gestanden* / *hat gesprochen* / *hat geschwiegen* / *ist geschritten* / *ist gelaufen*)

In general, making use of the vowel gradation (Ablautreihe) is so much easier to achieve physiopsychologically while speaking that one could also quite often hear new *Starke Verben* being produced, that is new irregular verbs created ad-hoc.