New verbs in English are invariably regular. Sneak, an old verb in English dating from the 16th century, is one of the very few that have, at least in some parts of the world, become irregular (with snuck now competing with sneaked), and only in the last 100 years.
Are there any truly new arrivals (by which I mean only to exclude established verbs with new prefix uses) of irregular or strong verbs in German?
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 principles that brought about these irregular verbs were only actively applied 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.
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 wave) which is most likely to enter eventually into generally accepted usage (if it hasn’t already) to coexist then with the regular 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 the ignorance of possible differences:
hängen/hing/gehangen vs. hängen/hängte/gehängt: The 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 ignore the origin of the word ableiten (to differentiate) and say things like abgelitten. I would say this is just a spleen with various individuals coming from mathematical professions because they likely 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) genossen (enjoyed) instead of geniest (sneezed).
schleifen/schliff/geschliffen vs. schleifen/schleifte/geschleift: Sometimes people mix up the former (meaning to hone, e.g. a piece of metal) with the latter (meaning to slight, e.g., a fortress).
It is also quite often the case that the past participle in German is produced erroneously while the main point to look at here is the actual intention of 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 used with a different past participle in German. For example, abgeschaltet vs. abgeschalten (to switch off [e.g. the television]) stems from the regular verb schalten which is conjugated with either of the two auxiliary verbs in German (sein/haben). It should be conjugated accordingly as follows:
Der Fernseher ist abgeschaltet.
Der Fernseher hat abgeschaltet.
There is also the tendency to use:
*Der Fernseher ist abgeschalten.
This stems in all likelihood from the non-obvious difference in usage of the auxiliary 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.
Many English verbs in the IT are not translated in the current German. For example
Their perfekt-form should be "gescannt", "gepusht", and so on, if they would be used as regular verbs. But they are not. My current experience is that many native German speakers build a half German/half English version of the perfekt-form: "gescanned", "gepushed" and so on.
These can be considered irregular verbs, although maybe regular, but half-English verb would be more accurate.
I taught German at an American university and the faculty used the verb “droppen” to express the concept of dropping a class - “Wieviele haben schon gedroppt?”.
As an kind of inside joke, some of us made it (very oddly) irregular: droppen drap gedrupt - ich droppe, du dröpst, usw. There was also a competing faction in the department that preferred “dropieren” :)
