"Come, sit, eat and go."
Translation:आओ, बैठो, खाओ और जाओ।
Is the imperative of 'to sit' irregular? The other verbs in this sentence add 'oo'
Not exactly irregular.
बैठ ('baiṭh') has a consonant ending due to schwa deletion (ie, the 'a' vowel attached to ठ is not pronounced). To make the तुम-form of the infinitive, we add ओ to this. Adding ओ to the vowel-less consonant ठ् would make it ठो, making the word बैठो.
Many verbs have a similar imperative form - देखो (see), सुनो (hear), सोचो (think), तैरो (swim), रहो (stay) etc