Step 1: Understanding the Question:
The question asks us to identify the psychosexual developmental stage in Sigmund Freud's theory where fixation leads to an adult personality characterized by excessive orderliness, neatness, and fussiness.
Step 2: Detailed Explanation:
• Sigmund Freud's psychosexual theory postulates that childhood development occurs in stages: Oral, Anal, Phallic, Latency, and Genital.
• The anal stage (from roughly $1.5$ to $3$ years) focuses on pleasure derived from retaining and expelling feces, coinciding with toilet training.
• If toilet training is conducted in an excessively harsh, punitive, or rigid manner, the child may experience fixation at this stage.
• This fixation results in an "anal-retentive" adult personality, characterized by being overly neat, tidy, orderly, stubborn, stingy, and fussy.
• Conversely, a lenient approach can lead to an "anal-expulsive" personality, characterized by messiness, disorganization, and carelessness.
• Oral fixation typically leads to dependence, overeating, or smoking; Phallic fixation centers on Oedipal conflicts and gender identity; the Genital stage represents mature adult relationships.
Step 3: Final Answer:
Fixation during the Anal stage of psychosexual development results in an excessively neat, tidy, and fussy adult personality.